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.

   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
2. 2.

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

   1 A

3. 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	?

4. 3.

   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
5. 4.

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

   • About 8 mA
   • About 4 mA
   • About 2 mA
6. 5.

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

   • The currents differ
   • The turns stay at 50
   • The speed stays the same
7. 6.

   How does a generator make a current, Milo?

   • It stores charge in a magnet
   • It heats a wire
   • It spins a coil in a magnetic field
8. 7.

   A coil spins steadily in a generator. What kind of current does it make, Noah?

   • Alternating current that reverses each half turn
   • A steady current in one direction
   • No current until it stops
9. 8.

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

   • Electrical to kinetic
   • Kinetic to electrical
   • Light to kinetic
10. 9.

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

    • It drops to one-tenth
    • It stays the same
    • It rises 10 times too
11. 10.

    Why does a real transformer get slightly warm, Zee?

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