Assorted Problem Set on Currents

See the attached file.
1. a) The magnitude of the earth's magnetic field at the surface of the earth is slightly less than one gauss.( I answered False and the answer was true)

b) The torque exerted on a current loop by a uniform field tends to orient the plane of the loop perpendicular to the magnetic field.(I answered false and the answer was true)

7. Doubling the number of loops of wire in a coil produced what kind of change in the induced emf assuming all other factors remain constant?
a. the induced emf quadruples
b. the induced emf is reduced by one-half
c. the induced emf doubles
d. there is no change in the induced emf
The other students answered C and I answered D.

9. If the emf induced in an inductor doubles, the self inductance of the coil.
a. doubles
b. halves
c. remains the same
d. quadruples
I answered D and the other students answered C.

12. Two parallel conductors each of 0.5m length, separated by 5*10^-3m and carrying 3.0 Amps in opposite directions, will experience what force on each other?
a. attractive, 0.06*10^-4 N
b. repulsive, 0.60 * 10^-4 N
c. attractive, 1.8*10^-4 N
d. repulsive, 1.8*10^-4 N
e. none of the above
I answered B the rest of the students answered D.

15. An electron is released such that its initial velocity is from right to left across this page. The electron's path, however, is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field. What is the direction of this field?
a. out of the page
b. into the page
c. from bottom edge to top edge of the page
d. from right to left across the page
e. None of the above
I answered C the other students answered A.

17. A current in a long, straight wire produces a magnetic field. The magnetic field lines:
a. go out from the wire to infinity
b. come in from infinity to the wire
c. form circles with pass through the wire
d. form circles which go around the wire
e. none of the above
I answered A the other students answered D.

18. A circular coil with an area of 0.0500m^2 is wrapped with 500 turns of wire and is placed in a uniform magnetic field perpendicular to its plane. If the field changes in value from 0.100T to 0.350T in an interval of 0.500s, what average voltage is induced in the coil.
a. 12.5V
b. 125V
c. 188V
d. 250V
I answered D the correct answer was A.

19. A bar magnet is falling through a loop of wire with constant velocity with the north pole entering the loop first. Viewed from the same side of the coil as the magnet enters, as the north pole enters the wire, the induced current will be in what direction?
a. clockwise
b. counterclockwise
c. zero
d. along the length of the magnet
I answered A the correct answer was B.

21.The emf induced in a circuit is proportional to the magnetic flux through the circuit.(I answered True the correct answer was False)

22. The inductor acts like an open circuit at very high frequencies.
( I answered False the correct answer wasTrue)

23. The force between two parallel wires that have currents running in the same direction is attractive.(I answered False the correct answer is True)

25. When energy is expended in operating an RLC circuit, which dissipates the most energy.
a. the capacitor
b. the inductor
c. the resistor
d. It depends on the relative values of the resistor, the capacitor and the inductor.
I answered D the correct answer was C.