AP Physics 2 electric circuits, magnetism, and geometric and physical optics concepts explained conceptually.
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- What does Ohm's Law state?
- V = IR: the voltage across a conductor equals its resistance times the current through it.
- Define electric resistivity and its SI unit.
- Resistivity is a material property measuring how strongly it opposes current flow; SI unit is ohm-meter (Ω·m).
- How does resistance depend on resistivity, length, and cross-sectional area?
- R = ρL/A, where ρ is resistivity, L is length, and A is cross-sectional area.
- What is the definition of electric current?
- The charge flowing past a point per unit time; I = Q/t, measured in amperes (A).
- Define capacitance and its SI unit.
- The ability of a device to store charge per unit voltage; C = Q/V, measured in farads (F).
- For a parallel-plate capacitor, how does capacitance depend on plate area and separation?
- C = ε0(εr)A/d, where A is plate area, d is separation, and ε0 and εr are permittivity constants.
- What is the difference between resistors in series versus parallel?
- Series: resistances add (R_total = R1 + R2 + ...); Parallel: reciprocals add (1/R_total = 1/R1 + 1/R2 + ...).
- State Kirchhoff's Current Law.
- The sum of currents entering a junction equals the sum of currents leaving the junction.
- State Kirchhoff's Voltage Law.
- The sum of voltage drops around any closed loop in a circuit equals zero.
- What is the time constant for an RC circuit and what does it represent?
- τ = RC; it is the time for the charge or current to decay to 1/e of its initial value.
- Define magnetic force on a moving charge and give its formula.
- F = qvB sin(θ), where q is charge, v is velocity, B is magnetic field strength, and θ is the angle between v and B.
- State the right-hand rule for magnetic force on a current-carrying wire.
- Point fingers in the direction of current, curl them toward the magnetic field direction; thumb points in the direction of force.
- What is the magnetic force on a current-carrying wire in a magnetic field?
- F = BIL sin(θ), where B is field strength, I is current, L is wire length, and θ is angle between wire and field.
- Define magnetic field strength B and its SI unit.
- The strength of a magnetic field, measured in tesla (T), or weber per square meter (Wb/m^2).
- What is the magnetic field at the center of a long solenoid?
- B = μ0(μr)nI, where n is turns per unit length, I is current, and μ0 and μr are permeability constants.