Question 1

What is the relationship between voltage, current, and resistance in Ohm's law?

Accepted Answer

Ohm's law defines the relationship as V = I × R, where voltage (V) is measured in volts, current (I) in amperes, and resistance (R) in ohms. For a constant resistance, current is directly proportional to applied voltage and inversely proportional to resistance. This fundamental relationship allows calculation of any one quantity if the other two are known.

Question 2

How does a resistor behave differently from a light bulb in a circuit?

Accepted Answer

A resistor maintains approximately constant resistance regardless of voltage or current. A light bulb's resistance changes significantly with temperature—as the filament heats, resistance increases and current decreases. This temperature-dependent behavior causes the light bulb's current-versus-voltage plot to be nonlinear, unlike the straight-line relationship for resistors.

Question 3

Why does current flow in the opposite direction to electron movement?

Accepted Answer

Electrons carry negative charge and move through wires in the direction opposite to conventional current flow. Because electrons are negatively charged, their movement in one direction defines current as flowing in the opposite direction. This convention allows consistent description of current behavior throughout electrical circuits.

Question 4

What makes a light-emitting diode act as a one-way valve for current?

Accepted Answer

An LED allows current to flow only when voltage is positive and exceeds a threshold value. In the forward direction, current increases rapidly as voltage increases. In the reverse direction, no current flows regardless of voltage magnitude. This directional behavior demonstrates how an LED functions as a one-way valve, passing current through low resistance forward and blocking it in reverse.

Question 5

How does resistance affect current flow at a constant voltage?

Accepted Answer

According to Ohm's law, higher resistance reduces current flow at constant voltage. By placing a resistor in series with a device, you can limit current and prevent damage or reduce shock risk. For example, choosing a light bulb with appropriate resistance ensures a flashlight's batteries supply suitable current without burning out the bulb.

Question 6

What happens to a light bulb's resistance when it is first turned on?

Accepted Answer

When a light bulb is first turned on, the filament is at room temperature with relatively low resistance, causing current to jump to a high level initially. As the filament heats up, resistance increases significantly and current drops to a lower, constant value. This temperature-dependent resistance change explains why current is highest immediately after power is applied.

Question 7

What role does electric potential play in circuit operation?

Accepted Answer

A power supply or battery has positive and negative terminals that define high and low electric potential values. The difference between these potentials is voltage, which drives charge movement through the circuit. This voltage difference is essential for creating current flow, making electric potential fundamental to all circuit operation.

Investigation Ohm's Law for Ohmic and Nonohmic Conductors - Assessment Quiz