Magnetic field around a wire and inside a coil

Answer Key - Grade 11 Science Worksheet - Challenge Me

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

1. 1.

   Two long parallel wires 10 cm apart carry 5 A and 3 A in opposite directions. What is the field midway between them, to 0.01 μT, Esme?

   32 μT
2. 2.

   Two long parallel wires 20 cm apart carry 12 A and 4 A in opposite directions. What is the field midway between them, to 0.01 μT, Kira?

   32 μT
3. 3.

   A student says the field around a wire points away from it, like light from a bulb. Which reply fits OpenStax, Luz?

   • Yes; the field points outward, weakening as 1 ÷ r²
   • No; the field lines are circles around the wire
   • Yes; it points away from the wire on both sides
4. 4.

   A student says that tripling the distance from a long wire cuts its field to a ninth. Which reply fits B = μ₀I ÷ (2πr), Milo?

   • Yes; a wire's field falls as 1 ÷ r²
   • No; it falls to a third, since B falls as 1 ÷ r
   • No; it falls to a ninth for a solenoid
5. 5.

   A student says a longer solenoid with the same turns per meter and current has a stronger field inside. Which reply fits B = μ₀nI, Noah?

   • No; the same n and I give the same field
   • Yes; more total turns make a stronger field
   • Yes; the field grows with the solenoid's length
6. 6.

   A lab needs 5 mT inside a solenoid that can carry at most 2 A. Which turns per meter work, Pia? Use μ₀ = 4π × 10⁻⁷ T·m/A.

   • About 4000 turns per meter, to be safe at 1 A
   • About 1000 turns in total, at any length
   • About 2000 turns per meter
7. 7.

   A solenoid has 2000 turns per meter and carries 1.5 A. What field is inside, Ren? Use μ₀ = 4π × 10⁻⁷ T·m/A.

   • About 3.8 mT
   • About 1.9 mT
   • About 0.75 mT
8. 8.

   A 0.5 m solenoid has 500 turns and carries 3 A. What field is inside, Tala? Use μ₀ = 4π × 10⁻⁷ T·m/A.

   • About 7.5 mT
   • About 3.8 mT
   • About 1.9 mT

9. Read this first

   Use this

   Field-line diagram (example data): two long parallel wires 10 cm apart, both seen end-on.

11. 9.

    In the two-wire diagram, wire 2's current is reversed to out of the page. With equal currents, what is the field at M, Ari?

    • Pointing straight at wire 2
    • Twice one wire's field
    • Zero: the two fields cancel
12. 10.

    In the two-wire diagram, wire 1 carries 6 A and wire 2 carries 4 A. What is the field at M, 5 cm from each, Bo?

    Use the picture in question 9.

    • 40 μT
    • 8 μT
    • 80 μT