An 80 W fan, a 60 W bulb and a 500 W washing machine are operated for 15, 20 and 1 hr, respectively. The total electrical power units consumed are

Steps to Solve

1. Convert Power Ratings to Kilowatts

First, convert the power ratings of the devices from watts to kilowatts.

• Fan: $80 \text{ W} = 0.08 \text{ kW}$
• Bulb: $60 \text{ W} = 0.06 \text{ kW}$
• Washing Machine: $500 \text{ W} = 0.5 \text{ kW}$

2. Calculate Energy Consumed by Each Device

Next, calculate the energy consumed (in kilowatt-hours) by each device using the formula:

$$ \text{Energy} = \text{Power (kW)} \times \text{Time (hr)} $$

• Energy consumed by the fan: $$ E_{\text{fan}} = 0.08 , \text{kW} \times 15 , \text{hr} = 1.2 , \text{kWh} $$

• Energy consumed by the bulb: $$ E_{\text{bulb}} = 0.06 , \text{kW} \times 20 , \text{hr} = 1.2 , \text{kWh} $$

• Energy consumed by the washing machine: $$ E_{\text{washing machine}} = 0.5 , \text{kW} \times 1 , \text{hr} = 0.5 , \text{kWh} $$

3. Sum Up the Energy Consumption

Now, sum the energy consumed by all devices to find the total energy consumption:

$$ E_{\text{total}} = E_{\text{fan}} + E_{\text{bulb}} + E_{\text{washing machine}} $$

Substituting the values we calculated:

$$ E_{\text{total}} = 1.2 , \text{kWh} + 1.2 , \text{kWh} + 0.5 , \text{kWh} = 2.9 , \text{kWh} $$