Circuit Analysis Techniques for AP Physics C: E&M (2025)

Ohm’s Law

Describes the relationship between voltage (V), current (I), and resistance (R): V = IR.

Kirchhoff’s Current Law (KCL)

States that the total current entering a junction equals the total current leaving.

Kirchhoff’s Voltage Law (KVL)

The sum of all voltage differences around any closed loop in a circuit is zero.

Series Circuits

All components share the same current, but voltage divides among them.

Parallel Circuits

All components have the same voltage, while current splits among paths.

Voltage Divider Rule

Used to find voltage across a resistor in a series circuit; formula: Vx=Rx/Rtotal*Vs.

Current Divider Rule

Determines current through a branch in a parallel circuit; formula: Ix=Rtotal/Rx*I.

Thévenin’s Theorem

Any linear circuit can be represented as a single voltage source (Vth) in series with a resistance (Rth).

Norton’s Theorem

Represents a circuit as a current source (In) in parallel with a resistance (Rn).

Superposition Principle

Total response in a linear circuit with multiple sources equals the sum of individual responses from each source.

Nodal Analysis

Applies KCL to calculate voltages at nodes by creating equations for current entering and leaving each node.

Mesh Analysis

Uses KVL to analyze closed loops in circuits by setting up equations for voltages in each loop.

Maximum Power Transfer Theorem

Maximum power is delivered to a load when the load resistance (RL) matches the source resistance (Rs).

Source Transformation

Converts a voltage source in series with a resistor to a current source in parallel with the resistor, or vice versa.

Delta-Wye (Δ-Y) Transformation

Converts delta (Δ) resistor configurations to wye (Y) configurations and vice versa.

Capacitors

Store energy in an electric field, block DC, and allow AC with reactance decreases as frequency increases.

Inductors

Store energy in a magnetic field, oppose current changes, and have reactance that increases with frequency.

Impedance

Resistance in AC circuits that accounts for both resistance and reactance.

Reactance

Opposition to AC current flow caused by capacitors and inductors.

Transient Response

The behavior of a circuit when it switches from one steady state to another.

Frequency-Dependent Response

The behavior of circuits that changes with varying frequency in AC systems.