3. A motor operating at full speed draws a current of 2.0A when connected to a 110V source.
The motor has an armature resistance of 7.002. What is the back emf at full speed?
(a) 14V (b) 110V (c) 96V
(d) none of the above
4. A transformer connected to a 120V ac source has an output of 24V ac. If the primary coil
has 330 turns, how many turns of wire are there in the secondary coil?
(a) 24turns (b) 330turns (c) 66turns (d) none of the above
5. A motor designed to operate on 120V draws a current of 33A when it first starts up. At
its normal operating speed, the motor draws a current of 2.7A. What is the back emf at normal
operating speed?
(a) 9.8V (b) 130V (c) 110V (d) none of the above
6. A coil of wire contains 100 loops. The coil is rotated such that the flux changes from
20 x 10-4Wb to 26 x 10-4Wb in 1.5 × 10-2s. What is the average induced emf?
(a) 1.8V (b) 1.1V (c) 4.0V (d) none of the above
7. A 500-turn circular coil with an area of 1.54 × 10-2m² is perpendicular to a 0.060T field.
The magnetic field changes to 0.020T in the opposite direction in 0.12s. What is the average
emf induced in the coil?
(a) 0.0051V (b) .010V (c) 5.1V (d) none of the above
8. A compass placed on a table points south. In which direction should a conductor, placed
directly above the compass, carry current in order to reverse the direction of the compass needle?
(a) east to west (b) north to south (c) west to east (d) none of the above