When a certain a.c supply is connected to a lamp, it lights with the same…

Physics JAMB 2006

When a certain a.c supply is connected to a lamp, it lights with the same brightness as it does with a 12 V d.c battery. Then r.m.s value of the a.c supply is?

  • 12.0 V checkmark
  • 3.5 V
  • 17.0 V
  • 8.5

The correct answer is: A

Explanation

The r.m.s value of an a.c voltage/current is the value of the d.c. voltage/ current that will dissipate the same amount of energy in a given resistance as the a.c. Thus the r.m.s value of the a.c supply is 12v.
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