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United StatesPhysics C: Electricity and Magnetism

Unit 11: Electric Circuits

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do you reduce a network of series and parallel resistors to find currents and voltages?

Topic 11.5 Compound Direct Current Circuits: combine resistors in series and parallel to find equivalent resistance, currents and voltages in multi-resistor networks.
A calculus-based answer to AP Physics C E&M Topic 11.5, covering series and parallel resistor rules, equivalent resistance, reducing networks step by step, and voltage and current dividers.
10 min answer →

What is electric current, and how is it related to drift velocity and current density?

Topic 11.1 Electric Current: define current as the rate of charge flow and relate it to drift velocity, current density and charge carriers.
A calculus-based answer to AP Physics C E&M Topic 11.1, covering current as dQ/dt, conventional versus electron flow, current density, the microscopic model with drift velocity, and conservation of charge in a circuit.
10 min answer →

How is electrical power delivered and dissipated, and how does it relate to current, voltage and resistance?

Topic 11.4 Electric Power: calculate the power delivered or dissipated in circuit elements using P = IV and its resistive forms.
A calculus-based answer to AP Physics C E&M Topic 11.4, covering electrical power P = IV, the resistive forms, energy dissipated as heat, power in a real battery, and energy delivered over time.
9 min answer →

How does conservation of charge constrain the currents meeting at a junction?

Topic 11.7 Kirchhoff's Junction Rule: apply the junction rule (charge conservation) and combine it with the loop rule to solve multi-loop circuits.
A calculus-based answer to AP Physics C E&M Topic 11.7, covering the junction rule as charge conservation, writing node equations, counting independent equations, and combining junction and loop rules to solve networks.
10 min answer →

How does conservation of energy constrain the voltages around a circuit loop?

Topic 11.6 Kirchhoff's Loop Rule: apply the loop rule (energy conservation) to write voltage equations for multi-loop circuits.
A calculus-based answer to AP Physics C E&M Topic 11.6, covering the loop rule as energy conservation, sign conventions for EMFs and resistors, writing loop equations, and solving multi-loop circuits.
10 min answer →

How do resistance and resistivity arise, and what does Ohm's law say about them?

Topic 11.3 Resistance, Resistivity, and Ohm's Law: relate resistance to resistivity and geometry, apply Ohm's law, and distinguish ohmic from non-ohmic behavior.
A calculus-based answer to AP Physics C E&M Topic 11.3, covering Ohm's law, resistance from resistivity and geometry, the microscopic form J = sigma E, temperature dependence, and ohmic versus non-ohmic devices.
10 min answer →

How do charge, current and voltage evolve in time when a capacitor charges or discharges through a resistor?

Topic 11.8 Resistor-Capacitor (RC) Circuits: model the exponential charging and discharging of a capacitor through a resistor using the time constant.
A calculus-based answer to AP Physics C E&M Topic 11.8, covering the differential equation of an RC circuit, the exponential charge and discharge solutions, the time constant, and the initial and final behavior of the capacitor.
12 min answer →

What are the basic elements of a simple circuit, and how do EMF and internal resistance set the terminal voltage?

Topic 11.2 Simple Circuits: model a single-loop circuit with a source of EMF, internal resistance and a load, and find currents and voltages.
A calculus-based answer to AP Physics C E&M Topic 11.2, covering EMF, internal resistance, terminal voltage, single-loop analysis, schematic conventions, and ideal versus real batteries.
10 min answer →