physics

 In a transformer, two coils are wound around a common iron core. To operate properly the transformer requires

A. More turns in the secondary coil than in the primary coil
B. More turns in the primary coil than in the secondary coil
C. A direct current source connecting to the secondary coil
*D. An alternating current source connecting to the primary coil

9. Which device can be used to increase voltage from a source of direct current?

A. Generator
B. Electroscope
*C. Induction coil
D. Mass spectrometer

10. The transformer on a power pole steps down the voltage from 10,800 volts to 120 volts. If the secondary coil contains 360 turns, how many turns are found on the primary coil?

A. 603
B. 900
C. 15,000
*D. 32,400