1. There are several ways to induce an e.m.f. in a conductor. Which one of these will not work?
• A. Move a wire past a permanent magnet
• B. Place a strong magnet next to a coil
• C. Increase the strength of a magnetic field near a coil
• D. Move a magnet in and out of a coil
2. The magnetic flux cutting through a loop of wire is defined as ...
• A. (area of loop parallel to the field) × (magnetic field strength)
• B. (area of loop perpendicular to the field) × (magnetic field strength)
• C. (length of wire parallel to the field) × (magnetic field strength)
• D. (length of wire perpendicular to the field) × (magnetic field strength)
3. Which of these is the unit for magnetic flux?
• A. tesla
• B. coulomb
• C. weber
4. "The direction of the induced current in a conductor will be in such a direction so as to oppose the change in flux that created it." This law is called ...
• A. Lenz's Law
• C. Planck's Law
• D. Tesla's Law
5. The magnitude of the e.m.f. induced in a conductor is proportional to ...
• A. the change in the flux
• B. the rate of change of flux
• C. the change in the field strength
• D. the rate of change of field strength
6+7. The diagram shows a long wire placed in a magnetic field directed in to the screen. 6. Which of these answers correctly describes the direction of the induced current in the wire when it is moved upwards (up the screen), or moved to the right?

 moved upwards moved to the right A current to the right current to the left B no current current to the right C current to the right no current D current to the left no current

7. In the above diagram, If the field strength is B and the wire of length l is moved with a velocity v, the maximum induced e.m.f. will be E. The experiment is repeated with a shorter wire of length l/4 and moved at a velocity of 3v. To induce the same e.m.f. E in the wire the magnetic field strength must be:

• A. 12B
• B. B/12
• C. 4B/3
• D. 3B/4

8+9. A coil is rotated at a constant frequency f inside a magnetic field. The induced e.m.f. generated in the coil is shown in this diagram. The peak e.m.f. is E. 8. Which of these four graphs shows the induced e.m.f. when the coil is rotated at a frequency of 2f?
(Scales of axes are the same as original graph above). 9. The r.m.s. voltage induced in this coil when rotated at the higher frequency of 2f is:

A. 2E

B. E√2

C. E

 D. E √2