Energy changes when charges or magnets move in a field

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   Like charges of 25 nC and 40 nC sit 4 cm apart. With k = 8.9875 × 10⁹ N·m²/C², how much energy is stored, in μJ, to 0.01, Bo?

   224.69 μJ
2. 2.

   Like charges of 10 nC and 10 nC sit 2 cm apart. With k = 8.9875 × 10⁹ N·m²/C², how much energy is stored, in μJ, to 0.01, Esme?

   44.94 μJ

3. Read this first

   Energy stored by two like charges at different distances (example data)

   Distance (cm)	Stored energy (μJ)
   2	45
   4	22.5
   8	11.25
   16	?

4. 3.

   Using the table, what happens to the stored energy each time the distance doubles, Jun?

   • It drops to one-quarter
   • It halves
   • It doubles
5. 4.

   Using the table, what energy should be stored at 16 cm, Kira?

   • 2.8125 μJ
   • 11.25 μJ
   • 5.625 μJ
6. 5.

   Using the table, the charges are released at 2 cm. What happens, Luz?

   • Nothing, since they are at rest
   • They pull together
   • They fly apart, gaining kinetic energy
7. 6.

   A compass needle is turned away from north and let go. Why does it swing back, Noah?

   • Its battery turns it
   • Air pushes it back
   • Field energy turns into its motion
8. 7.

   A toy train floats above a track on repelling magnets. What happens to the field energy if the train is pushed down closer, Pia?

   • It increases
   • It stays the same
   • It decreases
9. 8.

   An electron is released between a positive and a negative metal plate. What happens to its kinetic energy as it moves, Ren?

   • It stays at zero
   • It decreases
   • It increases
10. 9.

    A proton is released near the positive plate. Which way does it move, Tala?

    • Toward the negative plate
    • Toward the positive plate
    • It stays put
11. 10.

    As a charge speeds up between the plates, what happens to the stored field energy, Zee?

    • It drops by the kinetic energy gained
    • It rises by the same amount
    • It stays the same