AP Physics C: Electricity and Magnetism Flashcards: Kirchhoff's Junction Rule
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
What does the junction rule imply about the accumulation of charge at a junction?
It implies that electric charge is not created, destroyed, or stored at a junction; the flow of charge is continuous and conserved.
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What does the junction rule imply about the accumulation of charge at a junction?
It implies that electric charge is not created, destroyed, or stored at a junction; the flow of charge is continuous and conserved.
What fundamental conservation law is Kirchhoff's junction rule a consequence of?
Kirchhoff's junction rule is a direct consequence of the conservation of electric charge.
A current of 8A enters a junction and splits into two paths. If 3A flows through the first path, how much current flows through the second?
According to the junction rule ($\sum I_{in}=\sum I_{out}$), 5A must flow through the second path (8A = 3A + 5A).
What is the mathematical equation for Kirchhoff's junction rule?
The relevant equation is $\sum I_{in}=\sum I_{out}$, representing that the sum of currents in equals the sum of currents out.
How would you apply Kirchhoff's junction rule to describe a point in a circuit where two wires merge into one?
You would state that the current in the single outgoing wire is equal to the sum of the currents from the two incoming wires.
Currents I1 and I2 enter a junction, while current I3 exits. Write an equation describing this situation using Kirchhoff's junction rule.
Based on the rule $\sum I_{in}=\sum I_{out}$, the equation for this junction would be I1 + I2 = I3.
A junction has one incoming current of 10A and two outgoing currents. If the outgoing currents are equal, what is the value of each?
The total outgoing current must be 10A. Since the two paths are equal, each will have a current of 5A.
Why is it accurate to say the junction rule is about the flow of charge?
The rule equates the total charge entering a junction per unit time with the total charge exiting per unit time, which is the definition of electric current.
State Kirchhoff's Junction Rule.
The total amount of current (charge per unit time) entering a junction must equal the total amount of current exiting that junction.
What is a 'junction' in the context of Kirchhoff's rule?
A junction is any point in an electrical circuit where three or more conductors meet, allowing current to split or combine.