Question

What is the r.m.s. value of an alternating current which when passed through a resistor produces heat which is four times of that produced by a direct current of 3 ampere in the same resistor?

Options

• 6 A

• 2 A

• 3 A

• 18 A

Answer 1

6 A

Explanation:

Heat produced by A.C. = 4 x Heat produced by D.C

`therefore "i"_"rms"^2 = 4 xx "I"^2 "Rt"`

`"i"_"rms"^2 = 4 xx 3^2`

`therefore "i"_"rms" = 2 xx 3 = 6"A"`