Electric currents make magnetic fields

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A long straight wire carries 5 A. With μ₀ = 1.25663706127 × 10⁻⁶ N/A², what is its field 2 cm away, in μT, to 0.01, Ari?

   50 μT
2. 2.

   A long straight wire carries 3 A. With μ₀ = 1.25663706127 × 10⁻⁶ N/A², what is its field 1.5 cm away, in μT, to 0.01, Bo?

   40 μT
3. 3.

   A long straight wire carries 12 A. With μ₀ = 1.25663706127 × 10⁻⁶ N/A², what is its field 3 cm away, in μT, to 0.01, Esme?

   80 μT

4. Read this first

   Paper clips lifted by a coil around an iron nail (example data)

   Turns	Current (A)	Clips lifted
   10	1	2
   20	1	4
   40	1	8
   20	2	?

5. 4.

   Using the table, how does the number of turns change the clips lifted at 1 A, Jun?

   • Twice the turns, half as many clips
   • Turns make no difference
   • Twice the turns, twice the clips
6. 5.

   Using the table, about how many clips should 20 turns lift at 2 A, Kira?

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

   Why use an electromagnet rather than a permanent magnet for lifting, Noah?

   • It is weaker
   • It can be switched on and off
   • It needs no electricity
8. 7.

   In an electric doorbell, what pulls the striker toward the bell, Pia?

   • An electromagnet
   • A spring pulling by itself
   • Static charge
9. 8.

   A compass sits under a wire. When the current is switched on, the needle turns. What turns it, Ren?

   • Heat given off by the wire
   • The current's magnetic field
   • Static charge
10. 9.

    The current in that wire is reversed. Which way does the needle turn now, Tala?

    • It doesn't turn
    • The same way
    • The opposite way
11. 10.

    A bigger current flows through the wire. What happens to the needle's turn, Zee?

    • It turns less far than before
    • It turns farther
    • It stops turning