Question

Two identical heaters, each marked $1000W,250V$ are placed in parallel with each other and connected to a $250V$ supply. Their combined rate of heating will be:

• A. $250W$
• B. $500W$
• C. $1000W$
• D. $2000W$

Answer 1

Answer: (D)

$2000W$

Each bulb is rated as $1000W,250V$.

Resistance of each heater $R=\frac{V^2}{P}$

$\therefore$ $R=\frac{(250{)}^2}{1000}=62.5\Omega$

As both the heaters (resistors) are connected in parallel, thus equivalent resistance of the combination is equal to half of the individual resistance.

Equivalent resistance of the parallel combination $R_p=\frac{R}{2}$

$\therefore$ $R_p=\frac{62.5}{2}=31.25\Omega$

Combined rate of heating $P_p=\frac{V^2}{R_p}$

$⟹$ $P_p=\frac{(250{)}^2}{31.25}=2000W$