Practice Generator in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

A device that converts mechanical (kinetic) energy into electrical energy by rotating a coil of wire within a magnetic field, exploiting electromagnetic induction.

Spin a loop of wire between magnets and you get electricity — the changing flux induces a voltage that drives current through an external circuit.

Showing a random 20 of 50 problems.

Example 1

challenge
A generator delivers 5 kW at 250 V RMS through a 1 Ω transmission line. By what factor does line loss change if the same power is sent at 2500 V RMS?

Example 2

hard
A power-station generator produces 25 kV RMS at 50 Hz. If the coil has N=500 turns in B=1.2 T, find the coil area.

Example 3

easy
A coil: N=10, B=0.5 T, A=0.2 m2, ω=4 rad/s. Find the peak EMF.

Example 4

hard
An AC generator's coil normal makes angle θ=ωt with B⃗. Show why the EMF magnitude is NBAω∣sin⁡(ωt)∣, not cos⁡.

Example 5

medium
A generator coil has 100 turns and area 0.05 m2 in a 0.4 T field. It needs to produce a peak EMF of 500 V. At what frequency must it rotate?

Example 6

medium
A generator's instantaneous EMF is E(t)=170sin⁡(120πt) V. What is the frequency?

Example 7

easy
A friend says a generator 'makes energy from spinning.' What is wrong with this statement?

Example 8

hard
A hydroelectric generator produces 10 MW at 20,000 V RMS. What RMS current does it deliver? If the transmission line has 2 Ω resistance, what percentage of power is lost in transmission?

Example 9

medium
A generator must produce a peak EMF of 200 V. Given B=0.5 T, A=0.04 m2, ω=100 rad/s, find the required number of turns.

Example 10

easy
What component must be added to a simple AC generator's coil terminals to make it output direct current?

Example 11

medium
True or false: a generator with a stationary coil and rotating magnet can also produce an EMF.

Example 12

medium
A generator coil has N=80 turns, area A=0.02 m2, in a field B=0.6 T, and spins at f=60 Hz. Find the peak EMF.

Example 13

hard
A wind-turbine generator rotates at ω=12 rad/s with N=300, B=0.8 T, A=1.5 m2. Find the average power dissipated in a 50 Ω load.

Example 14

easy
A coil with N=25, B=0.2 T, A=0.1 m2 rotates at ω=8 rad/s. Find the peak EMF.

Example 15

medium
A generator coil with peak EMF 80 V drives a 20 Ω resistor. Find the peak current and RMS power dissipated.

Example 16

easy
Name the physical principle a generator relies on to convert mechanical motion into an EMF.

Example 17

medium
A coil: N=50, B=0.4 T, A=0.1 m2, ω=10 rad/s. Find the peak EMF.

Example 18

medium
A 4-pole AC generator rotates mechanically at fmech=30 Hz. What electrical frequency does it produce? (felec=(pole pairs)fmech.)

Example 19

hard
A generator coil drives a 40 Ω load with Vrms=110 V. The coil + connecting wires have internal resistance 5 Ω. Find the load's average power.

Example 20

challenge
A generator delivers 120 V RMS to a 10 Ω load. Find the average power dissipated. (P=Vrms2/R.)
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