Energy changes when charges or magnets move in a field

Answer Key - Grade 11 Science Worksheet - Building Confidence

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

1. 1.

   An average pull of 2 N separates two attracting magnets by 0.05 m. How much energy is stored in their field, Ari?

   0.1 J
2. 2.

   An average pull of 0.8 N separates two attracting magnets by 0.03 m. How much energy is stored in their field, Bo?

   0.024 J
3. 3.

   An average pull of 4.5 N separates two attracting magnets by 0.02 m. How much energy is stored in their field, Esme?

   0.09 J

4. Read this first

   Use this

   Energy bar chart (example data), one bar per energy store, height in J. Touching: field energy 0 J; kinetic 0 J. Pulled 4 cm apart and held: field energy 0.06 J; kinetic 0 J. Let go, just before they meet: field energy 0 J; kinetic 0.06 J. Two magnets attract, north pole facing south pole; field lines run from the north pole to the south pole between them.

5. 4.

   In the energy bar chart, how much energy is stored once the magnets are pulled 4 cm apart, Jun?

   • 0.06 J
   • 0.24 J
   • 0 J
6. 5.

   In the energy bar chart, where does the stored energy go after the magnets are let go, Kira?

   • Into more field energy
   • It disappears
   • Into the magnets' kinetic energy
7. 6.

   In the energy bar chart, where did the stored field energy come from, Luz?

   • Heat from the room
   • The magnets' weight
   • The work done pulling them apart
8. 7.

   Two attracting magnets are let go and snap together. What happens to their field energy, Noah?

   • It stays the same
   • It is released
   • It increases, since they pull harder
9. 8.

   Two magnets are pushed together with north facing north. What happens to their field energy, Pia?

   • It increases
   • It is released
   • It drops to zero
10. 9.

    Near a magnet's poles, the field lines are crowded together. What does that show, Tala?

    • There is no field there
    • The field is strongest there
    • The field is weakest there
11. 10.

    Which way do electric field lines run between a positive and a negative charge, Zee?

    • In circles around each charge
    • From negative to positive
    • From positive to negative