Question

A lamp of $100W$ and a heater of $1kW$ are in simultaneous use for $10hrs$. The units of electricity consumed according to the meter in the house are:

• A. $10$
• B. $9$
• C. $11$
• D. $1$

Answer 1

The correct option is C $11$

One $unit$ of electricity is $1kwh$.

For lamp, electrical energy consumed is,

$E_L=P_{L}t$

$\Rightarrow E_L=100\times 10$

$\Rightarrow E_L=1kWh$

$\Rightarrow E_L=1unit$

For heater, electrical energy consumed is,

$E_H=P_{H}t$

$\Rightarrow E_H=1000\times 10$

$\Rightarrow E_H=10kWh$

$\Rightarrow E_H=10unit$

Hence, total electrical energy consumed is:

$E=E_L+E_H$

$\Rightarrow E=(1+10)unit$

$\Rightarrow E=11unit$