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AP Physics C: Electricity and Magnetism Practice Quiz: Kirchhoff's Loop Rule

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 10 questions to check your progress.

Question 1 of 10

Kirchhoff's loop rule is a direct consequence of which fundamental physical principle?

All Questions (10)

Kirchhoff's loop rule is a direct consequence of which fundamental physical principle?

A) Conservation of charge

B) Conservation of energy

C) Conservation of momentum

D) Newton's Third Law

Correct Answer: B

The provided content explicitly states that Kirchhoff's loop rule is a consequence of the conservation of energy. As an electric charge moves around a closed loop and returns to its starting point, its potential energy must be the same, meaning the net change in electric potential (and thus energy) is zero.

Which of the following statements correctly defines Kirchhoff's loop rule?

A) The total current entering a junction must equal the total current leaving it.

B) The potential difference across a resistor is directly proportional to the current flowing through it.

C) The sum of potential differences across all circuit elements in a single closed loop must equal zero.

D) The electric potential in a circuit is always constant.

Correct Answer: C

This is the precise definition of Kirchhoff's loop rule as stated in the provided content. The rule is mathematically expressed as ΣΔV = 0 for any closed loop.

A simple closed circuit consists of a 12V battery and a single resistor. According to Kirchhoff's loop rule, what is the potential difference across the resistor?

A) +12V

B) 0V

C) -12V

D) It cannot be determined without the resistance value.

Correct Answer: C

According to Kirchhoff's loop rule, the sum of potential differences in the loop must be zero (ΣΔV = 0). The battery provides a potential increase of +12V. Therefore, the resistor must have a potential difference (drop) of -12V to make the sum zero: (+12V) + (ΔV_resistor) = 0.

Which equation is the correct mathematical representation of Kirchhoff's loop rule?

A) ΣI = 0

B) V = IR

C) P = IV

D) ΣΔV = 0

Correct Answer: D

The provided content explicitly gives the relevant equation for Kirchhoff's loop rule as ΣΔV = 0, which states that the sum of all potential differences (voltages) around a closed loop is zero.

A graph of electric potential versus position is created for a single closed circuit loop. If the rule is applied correctly, what must be true about the graph's starting and ending points?

A) The graph must start at zero and end at a positive value.

B) The graph must show a continuously increasing potential.

C) The graph must start and end at the same electric potential value.

D) The slope of the graph must be constant throughout the loop.

Correct Answer: C

Kirchhoff's loop rule (ΣΔV = 0) implies that after traversing a complete loop, the electric potential must return to its initial value. Therefore, a graph of potential vs. position for a complete loop must start and end at the same vertical (potential) level.

In a closed loop, a power source provides a potential increase of 9V. The loop also contains two resistors, R1 and R2. If the potential drop across R1 is 4V, what is the potential drop across R2?

A) 4V

B) 5V

C) 9V

D) 13V

Correct Answer: B

Using Kirchhoff's loop rule, ΣΔV = 0. We can write the equation for the loop as: +9V - 4V - ΔV_R2 = 0. Simplifying gives 5V - ΔV_R2 = 0, which means the potential drop across R2 must be 5V.

A student applies Kirchhoff's loop rule to a circuit and writes the equation: +ε - ΔV₁ - ΔV₂ = 0. Which of the following circuit descriptions matches this equation?

A) A circuit with three different power sources in series.

B) A circuit with a single power source and two other elements causing potential drops.

C) A circuit with three elements that all cause potential drops.

D) A circuit where the potential is zero everywhere.

Correct Answer: B

The equation represents one potential gain (+ε), likely from a battery or power source, and two potential drops (-ΔV₁ and -ΔV₂), likely across resistors or other components. The sum equals zero, correctly applying the loop rule.

A graph shows the electric potential in a circuit loop. The potential starts at 0V, rises to +6V, remains constant for a short distance, drops by 4V, and then drops by another 2V to return to 0V. This graph is a representation of:

A) Ohm's Law

B) The law of conservation of charge

C) Kirchhoff's loop rule

D) The quantization of electric charge

Correct Answer: C

The graph visually represents the changes in potential around a closed loop. The fact that the potential rises and then drops, ultimately returning to its starting value (0V), is a direct graphical illustration of Kirchhoff's loop rule (ΣΔV = 0).

The primary purpose of applying Kirchhoff's loop rule is to:

A) Calculate the total power dissipated by a circuit.

B) Determine the direction of the magnetic field.

C) Describe the potential differences within a closed circuit loop.

D) Measure the total charge flowing through a wire.

Correct Answer: C

As stated in the content, Kirchhoff's loop rule is used to 'describe a circuit or elements of a circuit' by summing the potential differences across all elements in a closed loop to zero. This allows for the analysis of voltages within the loop.

If you traverse a complete circuit loop and find that the sum of potential differences is not zero, what does this imply?

A) The circuit has no resistance.

B) Energy is not conserved in the circuit.

C) The loop is not actually closed, or there is a changing magnetic field.

D) The current must be zero.

Correct Answer: B

Kirchhoff's loop rule is a statement of conservation of energy. If the sum of potential differences is not zero, it would mean a charge could gain or lose energy by making a round trip, which violates the principle of conservation of energy in a standard electrostatic circuit.