Name: measuring voltage, current, and resistance
Uploaded: 2023-04-30T06:39:57.000Z
Duration: 12 min 41 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS+Phy.P4

HS+Phy.P4U1.8

investigation-ohm-s-law-for-ohmic-and-nonohmic-conductors

Investigation Ohm's Law for Ohmic and Nonohmic Conductors

1. Becoming Familiar with the Apparatus
<ol>
	<li>For this experiment, use a computer to collect the data and plot graphs.</li>
	<li>Load the software for the experiment by double-clicking on the "Ohm's Law" icon on the computer desktop. When the program loads, the screen should show a graph, a table, and in the lower right corner, boxes with the voltage and current readings.</li>
	<li>Click the Zero button and select "Zero All Sensors" to make sure that the voltage and current readings read zero when they are unconnected.</li>
	<li>Following the circuit diagram in Figure 1, connect the two leads on the voltage sensor to the power supply, which is a blue box. The red lead goes to the + connection on the power supply, and the black lead goes to the - one.</li>
	<li>Make sure that the current sensor is not connected, and ensure that the current knob on the power supply is turned to maximum (fully clockwise).</li>
	<li>Start the data collection by pressing the green arrow icon (the Collect button) on the computer.</li>
	<li>Observe what happens when the voltage knob on the power supply is moved between its minimum and maximum settings. Adjusting the knob allows the voltage to be changed from about +0.7 V to at least +5 volts.</li>
	<li>Reverse the leads of the voltage sensor (red to -, black to +), and repeat the steps 1.5-1.7. This time, adjusting the knob gives a voltage range of about −0.7 V to -5 V. Thus, by adjusting the power supply voltage as well as reversing the leads, almost the full range of voltages between -5 V and +5 V is available to work with in this experiment. Note that the power supply used in this experiment cannot put out voltages below 0.7 volts (an unusual feature), but there is more than enough of a range to determine the relationships of interest.</li>
</ol>
<img alt="Electrical circuit diagram with power supply, voltage sensor measuring potential difference." src="/files/ftp_upload/10116/10116fig1.jpg" data-altupdatedat="1761830439000" data-alt="Figure 1">
Figure 1: This circuit diagram shows the power supply (marked with the + and - symbols) and the voltage sensor (V) connected by two wires.
2. Investigating Ohm's Law
Note: In this part of the experiment, the goal is to observe graphs of current vs. voltage.
<ol>
	<li>To change what is displayed on an axis, click on the axis label, check the appropriate option to display the desired information, and (for the y-axis only) remove the check(s) for unwanted items on the display. Set the graph to show current on the y-axis and potential on the x-axis.</li>
	<li>To set the scales properly, click on one of the numbers to the left of the y-axis. This brings up a box to enter a minimum of -0.3 and a maximum of 0.3 for the manual scaling. Repeat for the x-axis by clicking on a number below the x-axis to bring up the settings box. This time, enter -6 as the minimum and 6 as the maximum. This prepares the graph to display currents between −0.3 and +0.3 A, and voltages between -5 V and +5 V.</li>
	<li>Following the circuit diagram in Figure 2, wire the circuit to measure the voltage and current across a 100 Ω resistor.</li>
	<li>Use a resistance box as the resistor. Set it for 100 Ω. On the power supply, turn both the current and the voltage to maximum.</li>
	<li>Press the green arrow icon to start the data collection.</li>
	<li>Over several seconds, turn the voltage down to minimum, then quickly reverse the leads at the power supply. Over several seconds, turn the voltage knob toward maximum again. This should result in a graph of current vs. voltage, ranging from about -5 volts to +5 volts.</li>
	<li>Repeat the process until satisfied with the graph, select the Data menu, and choose "Store Latest Run."</li>
	<li>Observe that the graph of current vs. voltage is a straight line. Hit the Regression button to perform a linear fit to the data, and record the slope of the line.
	<ol>
		<li>Figure 4 shows the current vs. voltage graph for the resistor marked 100 Ω. A linear fit to the data results in a slope of 0.00991 A/V. The inverse of the resistance is 0.0100 A/V, which is a good match to the slope.</li>
	</ol>
	</li>
	<li>Change the resistance of the resistance box to 200 Ω, and repeat the steps 2.6-2.9.</li>
	<li>Compare the two slope values to the corresponding resistance values, and determine the relationship between current, voltage, and resistance.
	<ol>
		<li>Figure 5 shows the current vs. voltage graph for the resistor marked 200 Ω. A linear fit to the data results in a slope of 0.00510 A/V. The inverse of the resistance is 0.00500 A/V, which is a good match to the slope.</li>
	</ol>
	</li>
	<li>The slope of the current vs. voltage graph turns out to be the inverse of the resistance. This can be written as: 
	<img alt="Ohm's Law, equation I=ΔV/R, illustrating current flow in a circuit." src="/files/ftp_upload/10116/10116eq1.jpg" data-altupdatedat="1761830439000" data-alt="Equation 1"> or <img alt="Ohm's Law equation ΔV=IR, fundamental electrical circuit principle, voltage-current relation" src="/files/ftp_upload/10116/10116eq2.jpg" data-altupdatedat="1761830439000" data-alt="Equation 2">
	<ol>
		<li>The current sent out by the power supply is proportional to the voltage and inversely proportional to the resistance. When the current is graphed as a function of the voltage, the slope of the line is expected to be the inverse of the resistance.</li>
	</ol>
	</li>
</ol>
 
<img alt="Electrical circuit with resistor, ammeter, and voltmeter for measuring current and voltage." src="/files/ftp_upload/10116/10116fig2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 2"> 
Figure 2: This circuit diagram shows the power supply connected to a 100 Ω resistor, with the voltage sensor (V) measuring the potential difference across the resistor and the ammeter measuring the current through it.
 
 <img alt="Electric circuit diagram; ammeter, voltage sensor; measuring current and voltage; educational use." src="/files/ftp_upload/10116/10116fig3.jpg" data-altupdatedat="1761830439000" data-alt="Figure 3"> 
Figure 3: In this circuit diagram, the resistor is replaced by a light bulb, and a switch has been added. The switch is initially open, so that the light bulb is off at the start. 
<img alt="Linear voltammetry graph showing current vs. potential; electrochemical analysis data." src="/files/ftp_upload/10116/10116fig4.jpg" data-altupdatedat="1761830439000" data-alt="Figure 4"> 
Figure 4: Current vs. voltage graph with a resistor marked 100 Ω. A linear fit to the data results in a slope of 0.00991 A/V. Note that the missing data at the center of the graph is simply an artifact of the particular power supply used in the experiment, which has the unusual feature of not producing voltages below about 0.7 V. <img alt="Linear I-V graph; current-potential relationship; electrochemistry; data analysis; scientific chart." src="/files/ftp_upload/10116/10116fig5.jpg" data-altupdatedat="1761830439000" data-alt="Figure 5"> 
Figure 5: Current vs. voltage graph with a resistor marked 200 Ω. A linear fit to the data results in a slope of 0.00510 A/V.
3. Investigating Light Bulbs
<ol>
	<li>Replace the resistor from the previous circuit with a small incandescent light bulb ( Figure 3). Repeat the experiment, obtaining a graph of current as a function of voltage for the light bulb. Note any differences in graph form for the light bulb compared to the resistor.
	<ol>
		<li>Figure 6 shows a graph of current vs. voltage for the incandescent light bulb. In general, the current increases as the voltage increases, but the graph is not nearly as linear as the graphs for the resistors. The graph also shows that the current is, in general, higher at a given voltage when the voltage is increasing, compared to its value at that same voltage when the current is decreasing.</li>
	</ol>
	</li>
	<li>Now, plot current vs. time instead of current vs. voltage. To do this, click on the "voltage" label on the horizontal axis to bring up the list of variables that the graph can be plotted against, and choose time instead of voltage.</li>
	<li>Turn the voltage up, so that the bulb glows brightly, and then switch the power supply off, using the on/off switch. Click on the Collect button (green arrow) on the screen to start the data collection, and switch the power supply back on.
	<ol>
		<li>Observe the graph, shown in Figure 7. The current through the light bulb goes to a high level when the power supply is switched on, and then drops to a smaller constant value. This is quite different than the behavior of a standard resistor, which would typically jump straight to a constant value when the power supply is turned on.</li>
		<li>The explanation for both of these observations is the same. The higher the temperature of the light bulb filament, the larger the resistance. When the bulb is off ( Figure 7), the filament is at room temperature with a relatively low resistance. When the bulb is then turned on, the current jumps to a high level because of the low resistance, but as the filament heats up and the resistance increases, the current drops. Eventually, the temperature stabilizes, and the current is constant.</li>
		<li>When the voltage is increasing ( Figure 6), the filament is warming up, so with a cooler filament the resistance is lower and the current higher. For the second half of the graph, when the voltage reduces, the filament is cooling down from a higher temperature, and thus has a higher resistance and lower current.</li>
	</ol>
	</li>
	<li>Finally, switch back to current vs. voltage, and use a LED in place of the light bulb.</li>
	<li>As before, obtain a graph of current as a function of voltage for the LED. Be sure to use both positive and negative voltages to see the full range of the circuit behavior with the LED.
	<ol>
		<li>Figure 8 shows the current vs. voltage graph for a LED. The diode does not allow current to flow in one direction, when the voltage is negative; however, when the voltage is positive and above a certain threshold, current flows and increases as quickly as voltage increases. In this way, the diode acts as a one-way valve for current. Note that the light-bulb filament and the resistors show no such directionality.</li>
	</ol>
	</li>
</ol>
<img alt="Cyclic voltammetry graph showing current vs. potential for electrochemical analysis." src="/files/ftp_upload/10116/10116fig6.jpg" data-altupdatedat="1761830439000" data-alt="Figure 6"> 
Figure 6: Current vs. voltage graph for an incandescent light bulb. The graph starts at the bottom left, then followed the upper track as the voltage was increased, and the bulb became very bright. The voltage was then decreased, and the graph followed the lower track back down to the bottom left.
<img alt="Electrochemical experiment graph showing current vs. time, illustrating transient current response." src="/files/ftp_upload/10116/10116fig7.jpg" data-altupdatedat="1761830439000" data-alt="Figure 7"> 
Figure 7: Current vs. time graph for an incandescent light bulb. The bulb was off, and then the voltage was turned on at around the 1.4 second mark and kept at a constant value. The current peaked at about 0.57 A, and then dropped down to a constant value of about 0.27 A.
<img alt="Electrochemical analysis graph; I-V curve showing current vs. potential relationship; voltammetry." src="/files/ftp_upload/10116/10116fig8.jpg" data-altupdatedat="1761830439000" data-alt="Figure 8"> 
Figure 8: Current vs. voltage graph for a diode. A diode, in some sense, acts as a one-way valve for current. The diode does not allow current to flow when the voltage is negative, but when the voltage is positive and above a certain threshold, the current flows and increases as quickly as voltage increases in one direction.

Electronic gadgets are omnipresent in today's world, and Ohm's law has a role to play in each of these gadgets. For instance, a flashlight designed to work on two 1.5-volt batteries in series (a total of 3 volts), must have a light bulb with an appropriate resistance, so that the batteries provide an appropriate amount of current to allow the bulb shine brightly, without burning out. Ohm's law helps guide that choice of bulb. 
Another application is a three-way light bulb, which can shine with...

investigation ohm's law for ohmic and nonohmic conductors

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment investigates Ohm's law, which relates current, voltage, and resistance.
One goal of the experiment is to become familiar with circuit diagrams and the terminology involved in basic circuits, such as resistor, resistance, current, voltage, and power supply. By the end of the experiment, familiarity is gained with how to wire up a circuit and how to measure both the current passing through a circuit component and the potential difference, or voltage, across it.
In a circuit, a battery or power supply provides a voltage measured in volts (V) that makes the charge flow. Other elements in the circuit, such as light bulbs or resistors (which are often just long narrow wires wound into coils) limit the rate at which the charge flows. The rate of flow of the charge is known as current measured in amperes (A), or amps for short, and the degree to which resistors and light bulb filaments limit the flow is known as their resistance measured in ohms (&#937;). This experiment involves an exploration of Ohm's law, which relates voltage, current, and resistance. 
This experiment also explores the difference between a basic circuit component called a resistor, and a light bulb and a light-emitting diode (LED). Light bulbs and LEDs are part of many common devices and are used for various lighting applications, and so it is useful to understand how they work.

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment investigates Ohm's law, which relates current, voltage, ...

Ohm's law relates voltage, current, and resistance for an electrical component, or a circuit.Voltage, V, current, I, and resistance, R, are fundamental to the operation of all electronic devices like radios, music players and computers as well as simpler electrical applications like house wiring, fuse boxes and home lighting. The circuits in all of these cases behave predictably and can be designed rationally because of Ohm's law.This video will introduce circuit terminology, symbols and diagrams, and then demonstrate how to wire a simple circuit. In addition, the current through a component and the voltage across a component will be measured.The output of a power supply or battery has both positive and negative terminals, which respectively define high and low values of a quantity called electric potential. The difference in this electric potential is voltage, measured in volts. To learn more about these terminologies, please see the video on electric potential in this collection.A circuit is a network of components connected together to perform a particular function. Current is the movement of a quantity of charge per second and is measured in amperes, or amps, for short. Interestingly, only electrons, which have negative charge, move through wires in a circuit. Because of their negative charge, electrons flow in the direction opposite to that of current. Electrical current can only flow through wires and components connected in a complete loop, much like water current from a reservoir through a pump, into a water wheel and back into the reservoir.To some degree all electrical elements impede the flow of current, like the bottleneck in a pipe that reduces the flow of water. Resistance describes this phenomenon, and is measured in ohms. Ohm's law defines resistance as voltage across a component divided by current through the component.For components specifically called resistors, the resistance is approximately constant. The resistor on a common circuit board is typically a small cylindrical object with bands representing a color code for the resistance. By Ohm's law, the current through a constant resistance is directly proportional to the applied voltage and inversely proportional to resistance. In reality, the resistance of most materials generally increases as temperature increases.The resistance of some devices, like diodes, also varies with the operating condition-that is, voltage and current-as well as other factors. A diode is a device that, to a very good approximation, allows current to flow in one direction only. As a result, it behaves as a one-way valve, passing current through a very low resistance in the "forward" direction and prohibiting current with an extremely high resistance in "reverse."A light emitting diode, also known as an "LED", is a diode that is illuminated with the flow of forward current. Like a simple diode, an LED does not pass current in the reverse direction, in which case it is not illuminated.With a simple relationship among voltage, current and resistance, Ohm's law-often expressed as V equals I times R-makes it possible to calculate any one of these quantities if the other two are known.This video will show that the voltage across a component and the current through it may be easily measured. These experiments will also demonstrate Ohm's law in various circuits and illustrate the relationship between current and voltage for a resistor, a light bulb, and a light emitting diode.The measurement apparatus consists of a voltage sensor, a current sensor, a power supply, a computer controlled measurement system, and the components to be tested.To load the measurement software, double-click on the "Ohm's Law" icon on the computer desktop. After the program loads, the screen should display a graph, a table and in the lower left corner, boxes with the voltage and current measurements.Click the "Zero" button and select "Zero All Sensors" to remove offsets in the data acquisition system. Voltage and current readings should be zero when the leads to the apparatus are not connected to anything.Select the data that will be plotted by clicking on the axis label and checking the desired option. For the y-axis only, uncheck items that will not be plotted. Set the graph to show current on the y-axis and voltage on the x-axis.Next, set the y-axis scale to negative 0.3 to positive 0.3 amps, and set the x-axis scale to negative 5 to positive 5 volts.A resistance box, which can be set for different values of resistance, is used in the first experiment in order to observe how current varies with voltage for a resistor.Set the resistance box to 100 ohms. Then wire together the power supply, voltage and current sensors, and resistance box as shown in the circuit diagram. Finally, set both the current and voltage outputs of the power supply to the maximum values.Click the green arrow icon to start data collection. Slowly reduce the power supply voltage to its minimum value. Then, reverse the leads at the power supply and slowly increase the voltage back to its maximum value. This should result in a graph of current versus voltage, spanning the range from -5 to +5 volts. Repeat this process until the graph is free of noise, then store the data.For the 100 ohm resistance, the plot of current versus voltage is a straight line. Perform a linear fit to the data and record the slope of the line. The slope should be very close to 0.0100 amp/volt, the inverse of the resistance.Now set the resistance box to 200 ohms and repeat the experiment to obtain another plot of current versus voltage over the range of -5 to +5 volts. This time the slope should be very close to 0.00500 amp/volt, again the inverse of the resistance.For a constant resistance, Ohm's law states that current through the resistor is proportional to the applied voltage and inversely proportional to resistance. This is apparent in the data for both the 100 ohm and 200 ohm resistors.For the next experiment, replace the resistor box with a small incandescent light bulb, as shown in the schematic diagram. Set the voltage control on the power supply to maximum and begin data collection. Slowly reduce voltage to the minimum value then slowly increase voltage back to the maximum. The computer will display a plot of current versus voltage over the range of about +0.7 to +5 volts.Reverse the power supply leads, set the voltage control to maximum, and repeat the process of reducing the voltage to the minimum value and increasing it to the maximum value again. The computer will display a plot of current versus voltage over the range of about -0.7 to -5 volts.The plot of current versus voltage for the light bulb is not nearly as linear as for the resistors. The graph also shows that in general the current is higher at a given voltage when voltage is increasing, compared to what it is at the same voltage when voltage is decreasing.When the voltage is increasing, the filament is warming up. With a filament that starts cooler, the resistance is lower and the current is higher. When the voltage is decreasing, the filament is cooling down from a higher temperature, so it has a higher resistance and a lower current at the same operating point.Now plot current versus time instead of current versus voltage. To do this, change the horizontal axis to measure time.Adjust the voltage to its maximum, so the bulb glows brightly. Then turn off the power supply. Click on the green arrow to start data collection and then turn the power supply back on.Current through the light bulb is high immediately after the power supply is turned on, then drops to a lower, constant value. While the bulb is off, the filament is at room temperature and has a relatively low resistance.When the bulb is first turned on, the current jumps to a high level because of that low resistance. However, the resistance of the filament increases significantly with temperature-as the filament heats, resistance grows and current drops. Eventually its temperature stabilizes and current is constant.Finally, set the axis to display current versus voltage again and use a light-emitting diode-an "LED"-in place of the light bulb. The maximum current for common LED's is around 30 mA, so the current must be carefully monitored to prevent burning out the LED.Use the procedure from the prior experiments to obtain a graph of current as a function of voltage for the LED. First apply positive voltage across the LED, and adjust the power supply voltage from maximum to minimum. Then switch the power supply leads and adjust the voltage from minimum back to maximum to observe the directionality of the LED.The resulting plot shows that an LED allows current to flow only when the voltage is positive and greater than a certain threshold. Once the diode "turns on," current increases quickly as voltage increases. However, no current flows for negative voltage. This behavior demonstrates how an LED acts like a one-way valve for current.?Electronic gadgets are omnipresent in today's world, and Ohm's law has a role to play in every single one of these gadgets.For instance, the bulb in a flashlight is designed to work with two 1.5-volt batteries in series. Therefore, a light bulb with a suitable resistance must be chosen, so that the batteries provide an appropriate amount of current to make the bulb shine brightly, without burning out. Ohm's law helps guide that choice of bulb.Another application of Ohm's law is to limit the current supplied to a particular device, perhaps to reduce the risk of electric shock, or to protect the device itself. Ohm's law tells us that, for a given voltage, the higher the resistance, the lower the current. Therefore, by placing a resistance in series with the device, we can limit the current flowing through the device and thus prevent any potential damage.You've just watched JoVE's introduction to Ohm's law. You should now understand the relationship between the voltage across an electrical component, its resistance, and the resulting current through it, as well as the differences in the electrical behavior of resistors, light bulbs, and light emitting diodes. Thanks for watching!

Education

JoVE Science Education

Physics

Physics II

measuring voltage, current, and resistance

This experiment measures voltage, current, and resistance in basic electric circuits. It also builds skill with circuit diagrams and the terms resistor, resistance, current, voltage, and power supply.

Students learn how to wire a circuit and how to measure current through a circuit component. They also measure the potential difference, or voltage, across a component. These steps help connect circuit symbols with real parts in the lab.

A power supply or battery provides voltage, measured in volts (V), that drives charge through the circuit. Circuit parts such as resistors and light bulbs limit how fast the charge flows. Current is measured in amperes (A), or amps, and resistance is measured in ohms (Ω).

The experiment also compares a basic resistor with a light bulb and a light-emitting diode, or LED. Light bulbs and LEDs appear in many common devices and lighting applications. Studying them helps explain how these parts work in everyday circuits.

Measuring Voltage, Current, and Resistance

electric fields

Visualizing Electric Field Lines

Electric field lines show how a charged object affects the space around it. A source charge creates an electric field, and that field can exert electric force on another charged object called the test charge. The electric field is a vector at each point in space, so it has both size and direction. The electric field is the electric force per unit test charge placed at a point. If a charge is placed in that field, the force on it equals the charge times the electric field. This makes electric...

electric potential

Voltage, Fields, and Equipotential Surfaces

Voltage, or electric potential, describes electric potential energy per unit charge. It is a scalar quantity, and it helps explain many electrical effects. In practice, the difference in electric potential is what matters most. Changes in electric potential across space are linked to the electric field. That field can produce an electric force on a charge. In a resistor, the difference in electric potential between two points drives electric current flow. This experiment uses a volt meter and...

magnetic fields

Magnetic Fields from Magnets and Currents

Magnetic fields come from moving electric charges and from magnetic materials such as bar magnets. A current is one example of moving charge. The magnetic field made by a current can be calculated with the Maxwell equation. Bar magnets also create magnetic fields. In magnetic materials, the field comes from tiny charge movements inside the material. These fields can be shown with small compass needle magnets, which turn to line up with the magnetic field. Magnetic fields push on other moving...

electric charge in a magnetic field

Measuring the Electron’s Charge-to-Mass Ratio

Measuring the electron’s charge-to-mass ratio is the focus of this physics experiment. It recreates J. J. Thomson’s famous experiment from the end of the 19th century. Thomson used it to measure the charge-to-mass ratio of the electron. This work also connects to Robert A. Millikan’s oil-drop experiment a few years later. Millikan’s result gave a value for the charge of the electron. Together, these experiments let scientists determine the electron’s mass and charge for the first time. Those...

This experiment measures voltage, current, and resistance in basic electric circuits. It also builds skill with circuit diagrams and the terms resistor, resistance, current, voltage, and power supply. Students learn how to wire a circuit and how to measure current through a circuit component. They also measure the potential difference, or voltage, across a component. These steps help connect circuit symbols with real parts in the lab. A power supply or battery provides voltage, measured in...

series and parallel resistors

How Resistance Changes in Circuit Paths

Series and parallel resistor connections change how current and voltage behave in a circuit. This experiment shows how to find the total, or effective, resistance for each setup. It also uses Ohm’s law to relate voltage and current when the resistance is known. In a series circuit, resistors are wired one after the other. The same current flows through each resistor. Their voltages add together to make the total voltage, so the effective resistance is the sum of the individual resistances.

capacitance

Measuring Charge Storage in Capacitors

Capacitors store opposite charges on two conductors, such as two metal plates. This charge separation creates a potential difference, or voltage drop, between the conductors. In this experiment, commercial capacitors and a parallel plate capacitor are used to show how capacitance links charge and voltage. Capacitance is the proportionality factor between the amount of charge on each conductor and the voltage drop across it. When the voltage changes with time, the current flowing into the...

inductance

Magnetic Induction in Coils

Magnetic induction in coils is demonstrated with inductive coils and a voltmeter. A rod magnet is inserted into or pulled away from the core of a coil to create a brief electromotive force, or emf, in the coil. The voltmeter measures the resulting voltage change. The experiment also shows mutual inductance between two coils. When current in one coil is turned on or off, it can induce an emf in a nearby second coil. This makes the link between changing current and a voltage response clear. <br...

rc/rl/lc circuits

How RC, RL, and LC Circuits Change Over Time

RC, RL, and LC circuits show how current and voltage can change over time. These circuits combine resistors, capacitors, and inductors, which each behave differently in an electric circuit. A resistor dissipates energy and follows Ohm’s law, so its voltage is proportional to its current. A capacitor stores electrical energy. In a capacitor, current depends on how fast the voltage changes. An inductor stores magnetic energy. In an inductor, voltage depends on how fast the current changes. When...

semiconductors

Doping Silicon for p- and n-Types

Semiconductors conduct electricity in ways that depend on temperature and impurity level. Crystalline silicon is the most common semiconductor material. Pure semiconductors are usually not strong conductors, so they are often combined with a small amount of impurity to improve conductivity. This process is called doping. Donor impurities, such as phosphorus and arsenic, add electrons to silicon. Acceptor impurities, such as boron and aluminum, remove electrons from silicon. When acceptors take...

photoelectric effect

UV Light and Electron Emission

Photoelectric effect is the emission of electrons from a metal when light shines on it. The key idea is that the light must have a high enough frequency for its photons to carry enough energy. That energy increases with light frequency. This experiment shows the photoelectric effect with a charged zinc metal plate. The zinc is connected to an electroscope, which is an instrument that shows the presence and relative amount of charge. The plate is then exposed to either a regular lamp or...

reflection and refraction

Bending Light in Lenses and Materials

Light changes speed when it moves through different materials. When it crosses from one material to another, it may slow down or speed up. That change in speed makes the light bend. This bending is called refraction. Some of the light is also reflected at the boundary between the two materials. In special cases, the light can bend so sharply that it is completely reflected back into the material it came from. The lab explores the basic law of refraction and shows how this behavior affects...

interference and diffraction

Laser Slits Reveal Wave Patterns

Laser light can reveal wave behavior through interference and diffraction. These are common wave effects seen in many settings, from water waves to electromagnetic waves such as light. Interference happens when two waves of the same kind overlap. Their combined wave creates a repeating pattern of larger and smaller amplitude. Diffraction happens when a wave passes through an opening or moves around an object. In that case, different parts of the wave can interfere and produce a similar pattern...

standing waves

Standing Waves on a Slinky

Standing waves on a slinky show how wave superposition and reflection can create stable patterns. These waves, also called stationary waves, appear to stay in place even though the material is moving up and down. They are formed when two waves travel in opposite directions with the same frequency and amplitude. Standing waves are easy to spot in finite media. A plucked guitar string is a common example. Water in a lake and air in a room can also show this behavior. On a string fixed at both...

sound waves and doppler shift

Measuring Sound Speed with Motion

Sound waves and motion are the focus of this high school physics experiment. The lesson connects how sound travels through air with how the sound changes when the source moves. It also shows how to measure the speed of sound in air. Waves are disturbances that move through a material medium or through empty space. Light waves can travel through a vacuum and through some forms of matter. They are transverse waves, which means the oscillations are perpendicular to the direction of travel. Sound...

physics ii

This collection explores topics including electrostatics, magnetism, optics, wave-based oscillations, and electrical circuits; explaining underlying principles behind physical phenomena that have changed our world.

Measure voltage, current, and resistance in basic circuits while learning circuit diagrams, wiring, and how resistors, light bulbs, and LEDs behave.

Measuring Voltage, Current, and Resistance | JoVE K12

Andrew Duffy

Overview

Principles of Ohm&#8217;s law

Investigating Ohm&#8217;s Law for Ohmic Resistors

Investigating Ohm&#8217;s Law for Nonohmic Resistors

Applications

Summary

Energy and Work

Source: Ketron Mitchell-Wynne, PhD,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of ...

Power and Energy

Energy is the total work required to drive the current through the circuit.
A rise in voltage results in more work done, passing more current, resulting ...

Heat Flow and Specific Heat

Heat is a type of energy transfer that is caused by a temperature difference, and it can change the temperature of an object. Since heat is a form of ...

Mechanisms of Heat Transfer I

Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature ...

Mechanisms of Heat Transfer II

In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the ...

conduction-convection-and-radiation-problem-solving

Conduction, Convection and Radiation: Problem Solving

There are three methods by which heat transfer can take place: conduction, convection, and radiation. Each method has unique and interesting ...

testing-the-heat-transfer-efficiency-of-a-finned-tube-heat-exchanger

Testing the Heat Transfer Efficiency of a Finned-tube Heat Exchanger

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Heat exchangers transfer ...

using-tray-dryer-to-investigate-convective-conductive-heat

Using a Tray Dryer to Investigate Convective and Conductive Heat Transfer

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Dryers are utilized in ...

Transformers

A device that transforms voltages from one value to another using induction is called a transformer. A transformer consists of two separate coils, or ...

conservation-of-energy-approach-to-system-analysis

Conservation of Energy Approach to System Analysis

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
The purpose of ...

Dye-sensitized Solar Cells

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
Today&#39;s modern world requires the use of a large amount of energy. While ...

Batteries and Fuel Cells

A battery is a galvanic cell that is used as a source of electrical power for specific applications. Modern batteries exist in a multitude of forms to ...

Design, evaluate, and refine a device that works within given constraints to transfer energy within a system.

HS+Phy.P4U2.7

What is Energy?

The universe is composed of matter in different forms, and all forms of matter contain energy. &#xA0;The different forms of energy on Earth originate from ...

Thermodynamic Systems

A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or ...

Work

Work is done when energy is transferred from one object to another. In other words, work is when a force acts on something that undergoes a displacement ...

Kinetic Energy - I

It&#8217;s plausible to suppose that the greater the velocity of a body, the greater effect it could have on other bodies. This does not depend on the ...

Gravitational Potential Energy

Potential energy is not just a property of each object, but also a property of the interactions between objects in a chosen system. For each type of ...

Elastic Potential Energy

Elastic potential energy is the energy stored as a result of the deformation of an elastic object, such as the stretching of a spring. An object is ...

Work-energy Theorem

According to Newton&#x2019;s second law of motion, the sum of all the forces acting on a particle (net force) determines the rate of change in the ...

Power

The concept of work involves force and displacement; meanwhile, the work-energy theorem relates the net work done on a body to the difference in its ...

Phase Changes

Phase transitions play an important theoretical and practical role in the study of heat flow. In melting or fusion, a solid turns into a liquid; the ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Calorimetry

When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Internal Energy

The internal energy of a thermodynamic system is the sum of the kinetic and potential energies of all the molecules or entities in the system. The kinetic ...

Enthalpy

Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum ...

First Law of Thermodynamics

A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of ...

first-law-of-thermodynamics-problem-solving

First Law Of Thermodynamics: Problem-Solving

The first law of thermodynamics states that the change in internal energy of the system is equal to the net heat transfer into the system minus the net ...

using-differential-scanning-calorimetry-to-measure-changes-in-enthalpy

Using Differential Scanning Calorimetry to Measure Changes in Enthalpy

Source: Laboratory of Dr. Terry Tritt &#8212; Clemson University
Differential Scanning Calorimetry (DSC) is a method of thermodynamic analysis based on ...

Analyze and interpret data to quantitatively describe changes in energy within a system and/or energy flows in and out of a system.

HS+Phy.P4U1.6

Gel Purification

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, ...

Voltage

The movement of electrons in a conductor requires some form of energy or work, usually provided by an external force, like a battery. This force is called ...

Electrical Current

Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...

Ohm's Law

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm&#8217;s law. The current that flows ...

Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

Electrical Power

Electric power is the product of current and voltage, represented in units of joules per second, or watts. For example, cars often have one or more ...

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ...

power-dissipated-in-a-circuit-problem-solving

Power Dissipated in a Circuit: Problem Solving

The equivalent resistance of a combination of resistors depends on their values and how they are connected.
The simplest combinations of resistors are ...

Kirchhoff's Current Law

Kirchhoff&#39;s current law, or KCL, is based on the law of charge conservation. It states that the total current entering and leaving a node in a circuit ...

Kirchhoff's Voltage Law

Kirchhoff&#39;s voltage law, or KVL, is based on the principle of energy conservation.
It states that the algebraic sum of all voltages around a closed ...

Resistors In Series

A resistor is an ohmic device that limits the flow of charge in a circuit. Most circuits have more than one resistor. If several resistors are connected ...

Resistors In Parallel

Resistors are in parallel when one end of all the resistors are connected to a continuous wire of negligible resistance and the other end of all the ...

Combination Of Resistors

Electrical devices in any circuit can be connected either by series or parallel connections. Additionally, circuits can be connected involving both of ...

Equivalent Resistance

In circuit analysis, situations often arise where resistors are neither in series nor parallel configurations. To tackle such scenarios, three-terminal ...

Use mathematics and computational thinking to explain the relationships between power, current, voltage, and resistance.

Measuring Voltage, Current, and Resistance

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