# Day 126

1. A wire 60 cm long and carrying a current of 4.2 A is placed in a magnetic field where B=410 mT. The angle between the current and the field is 40o. What force does the wire experience?

Answer (.66N)

3. A solenoid with 900 turns of wire per meter of length carries 0.87 A of current. What is B at the center?

Answer (9.8 x 10^-4 T)

5. A proton is circulating in a cyclotron and requires a time T to make one revolution. In the same cyclotron, an alpha particle which has twice the charge and four times the mass of a proton would require a time of …

Answer (0.5 T)

7. A proton moves at 6.5 x 10^6 m/s in a direction perpendicular to a magnetic field where B=0.20T. What is the acceleration of the proton?

Answer (1.2 x 10-14 m/s2)

9. At the equator, the Earth’s magnetic field is nearly horizontal, has a magnitude of about 5.0 x 10-5T, and points from south towards north. What is the force it produces on a power line that is 500 m long and carries 100 A in a direction that is 45o east of north?

Answer (1.8 N)

11. The coil in a speaker has a diameter of 2 cm, contains 50 turns of wire, and is placed in a 150 mT magnetic field. The current in the coil is 1.7 A. (A) What magnetic force acts on the coil? (B) If the coil has a mass of 30 g, find its acceleration.

Answer (1.2 N, 40 m/s2)

(source)