The rms value of alternating current which when passed through a resistor produces heat energy four times that produced by directed current of 2 A through the same resistor in same time is

Options

A. 2A
B. 4A
C. 8A
D. 16A

Answer

B

Explanation

`H_(dc)=I_(dc)^(2)Rt=4Rt=W` . . . (1)
`H_(ac)=I_(ac)^(2)Rt=4W ` . . . (2)
`therefore (4W)/(W)=(I_(ac)^(2)Rt)/(4Rt)`
`therefore I_(ac)^(2)=16`
`therefore I_(ac)=4A`