Question

If two heaters, each of power $1kW$ are connected in parallel to a $250V$ supply, their combined rate of heating will be

• A. $1kW$
• B. $2kW$
• C. $5kW$
• D. $250W$

Answer 1

The correct option is B $2kW$

Power of each bulb = $1000W$

Voltage= $250V$ (as in parallel voltage remains same)

$P=\frac{V^2}{R}$

$1000=\frac{250\times 250}{R}$

$R=\frac{250}{4}\Omega$

Two resistance in parallel:

So equivalent resistance $=\frac{R+R}{R+R}$

Req$=\frac{R}{2}$

Req$=\frac{250}{8}\Omega$

Rate of heating $=\frac{V^2}{Req}$

$=\frac{250}{250}\times 8\times 250=2000W$

$=2kW$