What should be the value of resistance `R` in the circuit shown in figure so that the electric bulb consumes the rated power?

Options

A. `4.5 Omega`
B. `6 Omega`
C. `12 Omega`
D. None fo these

Answer

B

Explanation

(b) The electric bulb consumers the rated power if the voltage across electric bulb is `3 V`
i.e., "resistance across" `AB` is `4.5 Omega`
Resistance of bulb, `R_(b) = (V^(2))/(P_(b)) = (3^(2))/(0.5) = 18 Omega`
`(R R_(b))/(R_(b) + R) = 45 Omega, 18 R = (9)/(2) (18 + R) implies = 6 Omega`