AP Physics: Electromagnetic Induction and AC Circuits flashcards

Question 1

What is the process of creating an emf by changing the magnetic flux?

Accepted Answer

Electromagnetic induction

Question 2

What quantity tells how much magnetic field passes through a given area?

Accepted Answer

Magnetic flux

Question 3

What expression gives magnetic flux through an area A in a field B, where θ is the angle from the perpendicular to the area?

Accepted Answer

Φ = BA cos θ

Question 4

Which law gives the emf in a coil from the changing magnetic flux through it?

Accepted Answer

Faraday's law of induction

Question 5

In emf = −N ΔΦ/Δt, what does the minus sign express, and which law is it?

Accepted Answer

Lenz's law: the induced emf opposes the change in flux

Question 6

Which law says the emf induced in a coil works against the change in magnetic flux?

Accepted Answer

Lenz's law

Question 7

What is the drag produced by eddy currents called?

Accepted Answer

Magnetic damping

Question 8

What is a loop of current in a conductor that is caused by motional emf called?

Accepted Answer

Eddy current

Question 9

Which device produces electric energy from mechanical work by spinning a coil inside a magnetic field?

Accepted Answer

Electric generator

Question 10

What is the emf produced by a running motor that opposes the voltage powering it?

Accepted Answer

Back emf

Question 11

What device uses induction to change a voltage from one value to another?

Accepted Answer

Transformer

Question 12

What kind of transformer decreases voltage?

Accepted Answer

Step-down transformer

Question 13

What kind of transformer increases voltage?

Accepted Answer

Step-up transformer

Question 14

What equation says the secondary-to-primary voltage ratio of a transformer equals the ratio of turns in the two coils?

Accepted Answer

Transformer equation: Vs/Vp = Ns/Np

Question 15

What describes how effectively two devices induce emfs in each other?

Accepted Answer

Mutual inductance

Question 16

What describes how effectively a device induces an emf in itself?

Accepted Answer

Self-inductance

Question 17

What is a device with significant self-inductance called?

Accepted Answer

Inductor

Question 18

What is the unit of inductance?

Accepted Answer

Henry (H)

Question 19

What expression gives the energy stored in an inductor of inductance L carrying current I?

Accepted Answer

½LI²

Question 20

What is the characteristic time constant τ of a series RL circuit, in terms of L and R?

Accepted Answer

τ = L/R

Question 21

What do we call the way an inductor opposes a change in current?

Accepted Answer

Inductive reactance

Question 22

What is the formula for inductive reactance in terms of frequency f and inductance L?

Accepted Answer

X_L = 2πfL

Question 23

What is the formula for capacitive reactance in terms of frequency f and capacitance C?

Accepted Answer

X_C = 1/(2πfC)

Question 24

What is the AC analogue of resistance in a DC circuit?

Accepted Answer

Impedance

Question 25

How is impedance Z found from resistance R and the reactances X_L and X_C?

Accepted Answer

Z = √(R² + (X_L − X_C)²)

Question 26

What is the frequency at which a circuit's impedance is at a minimum called?

Accepted Answer

Resonant frequency

Question 27

What is the formula for the resonant frequency f₀ in terms of L and C?

Accepted Answer

f₀ = 1/(2π√(LC))

Question 28

What is the amount by which voltage and current are out of phase in a circuit called?

Accepted Answer

Phase angle (φ)

Question 29

What is the quantity, equal to cos φ, that says how far delivered power falls short of the maximum because voltage and current are out of phase?

Accepted Answer

Power factor

AP Physics: Electromagnetic Induction and AC Circuits flashcards

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