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. 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	?

4. 3.

   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
5. 4.

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

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

   Using the table, why do the first three rows make a fair test of turns, Luz?

   • The clips differ in each row
   • The current stays at 1 A
   • The turns stay at 20
7. 6.

   A crane lifts scrap steel with an electromagnet. How does it let the steel go, Milo?

   • It turns the magnet over
   • It adds more turns
   • It cuts the current
8. 7.

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

   • It is weaker
   • It needs no electricity
   • It can be switched on and off
9. 8.

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

   • Static charge
   • An electromagnet
   • A spring pulling by itself
10. 9.

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

    • Static charge
    • The current's magnetic field
    • Heat given off by the wire
11. 10.

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

    • The opposite way
    • The same way
    • It doesn't turn