A changing magnetic field makes a current: generators and transformers

Answer Key - Grade 11 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   An ideal transformer takes 0.5 A at 120 V and gives out 12 V. What current comes out, Ari?

   5 A
2. 2.

   At a substation, an ideal transformer takes 2 A at 240 V and steps it up to 6000 V for the power lines. What current comes out, Bo?

   0.08 A
3. 3.

   An ideal transformer takes 3 A at 12 V and gives out 36 V. What current comes out, Esme?

   1 A

4. Read this first

   Peak current as a magnet is pushed into a coil (example data)

   Push speed	Coil turns	Peak current (mA)
   slow	50	2
   medium	50	4
   fast	50	8
   medium	100	?

5. 4.

   Using the table, how does push speed change the peak current, Jun?

   • Speed makes no difference
   • Faster pushes give smaller currents
   • Faster pushes give bigger currents
6. 5.

   Using the table, about what peak current should 100 turns give at medium speed, Kira?

   • About 8 mA
   • About 4 mA
   • About 2 mA
7. 6.

   Using the table, why do the first three rows test speed fairly, Luz?

   • The turns stay at 50
   • The speed stays the same
   • The currents differ
8. 7.

   A bike's dynamo lights its lamp as the wheel turns. What energy change happens, Pia?

   • Light to kinetic
   • Kinetic to electrical
   • Electrical to kinetic
9. 8.

   An ideal transformer steps the voltage up 10 times. What happens to the current, Ren?

   • It stays the same
   • It rises 10 times too
   • It drops to one-tenth
10. 9.

    An ideal transformer takes in 100 W. How much power can it give out, Tala?

    • 0 W
    • At most 100 W
    • 1000 W, if it steps up 10 times
11. 10.

    Why does a real transformer get slightly warm, Zee?

    • Some energy turns to heat in its coils
    • Its magnet is hot
    • It makes extra energy