Practice Transformer in Physics

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

Quick Recap

A device that changes AC voltage using electromagnetic induction between two coils on a shared iron core.

A transformer trades voltage for current (or vice versa) — like a gear system trades speed for torque.

Showing a random 20 of 50 problems.

Example 1

medium
Why does a transformer hum and warm up even with no load connected?

Example 2

easy
A step-up transformer has 100100 turns on the primary coil and 500500 turns on the secondary coil. If the input voltage is 240 V240 \text{ V}, what is the output voltage?

Example 3

easy
True or false: an ideal transformer can amplify electrical power.

Example 4

easy
Why does the National Grid use very high voltages to transmit electricity?

Example 5

medium
An ideal transformer supplies 40 W40 \text{ W} at 20 V20 \text{ V} on the secondary. If the primary voltage is 240 V240 \text{ V}, find the primary current.

Example 6

medium
An ideal transformer: Vp=120V_p=120 V, Ip=2I_p=2 A, Vs=240V_s=240 V. Find IsI_s.

Example 7

challenge
A transmission line of resistance 5.0 Ω5.0 \text{ }\Omega delivers 100 kW100 \text{ kW}. Compare wire-loss percentage at 1000 V1000 \text{ V} vs 10,000 V10{,}000 \text{ V} delivery.

Example 8

medium
A transformer should output Vs=6V_s=6 V from Vp=120V_p=120 V with Ns=20N_s=20 turns. Find NpN_p.

Example 9

easy
Which physical law forms the underlying principle of a transformer's operation?

Example 10

medium
A transformer steps 240240 V down to 1212 V. If the secondary draws 55 A, find the primary current (ideal).

Example 11

medium
A transformer: Np=500N_p=500, Ns=100N_s=100, Vp=120V_p=120 V. Find VsV_s and identify the type.

Example 12

medium
A phone charger transformer converts 240 V240 \text{ V} AC to 5 V5 \text{ V} AC. If the primary coil has 960960 turns, how many turns does the secondary coil have?

Example 13

easy
In an ideal transformer, what quantity is conserved between primary and secondary?

Example 14

easy
A transformer has a turns ratio (secondary : primary) of 1:81:8 and Vs=24 VV_s = 24 \text{ V}. Find VpV_p.

Example 15

challenge
A transformer is 90%90\% efficient. The primary draws 200200 W. Find the output power and, if Vs=20V_s=20 V, the secondary current.

Example 16

medium
An ideal transformer: Vp=240V_p=240 V, Ip=1I_p=1 A, Vs=120V_s=120 V. Find IsI_s.

Example 17

hard
A transformer is 95%95\% efficient. The primary draws 2.0 A2.0 \text{ A} at 240 V240 \text{ V}. Find the secondary power output.

Example 18

easy
A transformer with more primary turns than secondary turns is which type?

Example 19

challenge
A transformer has Np=600N_p=600, Ns=150N_s=150. The secondary feeds a 5Ω5\,\Omega resistor. If Vp=240V_p=240 V (ideal), find the secondary current and the power delivered.

Example 20

medium
A bell circuit uses a transformer that steps 240 V240 \text{ V} down to 8 V8 \text{ V} to drive a 4 W4 \text{ W} bell. Find the primary current (assume ideal).