Question

A filament bulb 500 W, 100 V is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W . The value of R is :-

• A. 26$\Omega$
• B. 13$\Omega$
• C. 236$\Omega$
• D. 46$\Omega$

Answer 1

The correct option is A 26$\Omega$

$\begin{array}{c}IfR=r\\ P_{max}=\frac{E^2}{4r}\\ \rho =VI\\ I=\frac{\rho }{V_B}=\frac{500}{100}=5A\\ V_R=IR=\left(230-100\right)=5R\\ R=26\Omega \\ Hence,optionAisthecorrectanswer.\end{array}$