Which of the following devices may be used to step up the voltage in a d.c. circuit?
-
A.
a step-up transformer -
B.
a d.c. generator -
C.
a wattmeter -
D.
an induction coil
Correct Answer: Option D
Explanation
An induction coil is a transformer for producing high-voltage alternating current from a low-voltage direct current, consisting essentially of two concentric coils with a common soft-iron core, a primary coil with relatively few windings of heavy wire, and a secondary coil with many turns of fine wire. Excitation of the primary coil by rapidly interrupted or variable current induces high voltage in the secondary coil.