Ohm's Law
Ohm's Law - Related Videos
12:41
Investigation Ohm's Law for Ohmic and Nonohmic Conductors
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2023
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...
01:21
Ohm's Law
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2023
Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm’s law. The current that flows through most substances is directly proportional to the voltage applied to them. The German physicist Georg Simon Ohm (1787–1854) was the first to demonstrate experimentally that the current in a metal wire is directly proportional to the voltage applied. Any material, component, or device that obeys Ohm’s law, where the current through the device is...
01:19
Ohm's Law
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2026
Resistors are fundamental components in electrical circuits, often manufactured from metallic alloys or carbon compounds. They model a material's ability to resist the flow of electric current, a characteristic that is crucial in controlling and regulating electrical power within a circuit. This current-resisting behavior of resistors is governed by Ohm's law, which states that the voltage across a resistor is directly proportional to the current flowing through it. The constant of...
02:53
Beer's Law - Concepts
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2020
Absorbance and Fluorescence When light hits a substance, it is either absorbed, transmitted, or reflected. Typically, a substance interacts with a range of wavelengths of light, each one interacting with the molecules or atoms differently. A substance may absorb a specific range of wavelengths, reflect another range of wavelengths, and transmit the other wavelengths of light. When a molecule absorbs light, the energy is used in four different ways: (1) translation, which causes the molecule to...
02:38
Third Law of Thermodynamics
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2020
A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero. This limiting condition for a system’s entropy represents the third law of thermodynamics: the...
FAQs
With resistance held constant, the equation makes current directly proportional to applied voltage: doubling voltage doubles current, while halving it halves current. This predictable scaling lets circuit analysis isolate an unknown quantity by rearranging the relationship to find voltage, current, or resistance. The proportional response applies only while the component’s physical conditions remain constant.
A component behaves non-ohmically when its resistance changes as operating conditions change, so current no longer responds proportionally to voltage. Temperature variation is one important cause identified in the source material. In such cases, a single fixed resistance cannot describe the component across all conditions, and calculations based on a constant value may not accurately predict circuit behavior.
Constant physical conditions keep the resistance value stable while voltage and current are compared. If those conditions change, the component may develop a different resistance, altering the relationship between the measured quantities. Treating resistance as fixed is therefore a condition of the calculation, not merely a convenient assumption, especially when analyzing whether a material or component is ohmic.
Voltage, current, and resistance values calculated with the relationship provide the electrical quantities needed to anticipate how a component behaves under different operating conditions. Changing voltage or resistance changes the associated current, which in turn affects the component’s power behavior. This makes the principle useful for evaluating circuit operation and choosing suitable resistance values during design.
First identify the two known electrical quantities among voltage, current, and resistance. Then select the corresponding rearrangement of V = IR to calculate the unknown quantity, while checking that the component’s physical conditions remain constant. The resulting value can be used to analyze the circuit, compare expected and observed behavior, or support a resistor-selection decision.
Resistor selection begins by determining the voltage and current conditions required for the circuit, then using their relationship to calculate the resistance that fits those conditions. The chosen value can be evaluated against the component’s expected behavior and operating conditions. This approach helps match resistance to circuit needs rather than selecting a value without considering voltage and current.
Researchers can compare voltage and current under controlled, constant physical conditions and determine whether a consistent resistance describes the results. If the relationship remains proportional, the component shows ohmic behavior within those conditions. If temperature or another condition changes resistance, the results can reveal non-ohmic behavior and indicate that a fixed-resistance model is insufficient.