Question

The figure shows two bulbs with a resistance of $10\Omega$ with switches and a fuse connected to mains through a socket. How are the two bulbs joined and what is net resistance?

• A. In parallel, $20\Omega$
• B. in series, $20\Omega$
• C. In parallel, $5\Omega$
• D. In series , $5\Omega$

Answer 1

Answer: (C)

In parallel, $5\Omega$

The two bulbs are connected in parallel.

Given,

Resistance of each bulb, $R_1=R_2=R=10\Omega$

For two resistors connected in parallel

Equivalent resistance, $R_{eq}$

$\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}$

$\frac{1}{R_{eq}}=\frac{1}{10}+\frac{1}{10}$

$\frac{1}{R_{eq}}=\frac{2}{10}=\frac{1}{5}$

$R_{eq}=5\Omega$