Question

An electric bulb is rated as 50 W, 220 V. Calculate the energy consumed by the bulb in 20
minutes. Express your answer in kWh.

Answer 1

Given that, an electric bulb is rated as 50 W, 220 V.

We have to find the energy consumed by the bulb in 20 minutes.

From above data we have, power (P) = 50W and voltage (V) = 220V

Power is defined as work done upon time.

Power = 50W = 50/1000 kW

Energy is defined as the capacity of doing work.

Energy = Power × time

Before substituting the values in above formula, convert the time into seconds. To convert time into seconds, divide the given value by 60.

Time = 20 min = 20/60 = 1/3 sec

Now, substitute the values in the above formula

Energy = 50/1000 × 1/3

Energy = 1/60

Energy = 0.017 kW

Therefore, the energy consumed by the bulb in 20 minutes is 0.017 kW.

Answer 2

Given :

• Power of Electric Bulb (P) = 50 W
• Potential difference (V) = 220 V
• Time interval (t) = 20 mins

To Find :

• Energy Consumed by bulb

Solution :

We are given that the power given to the electric bulb (P) is 50 Watts. And potential difference is given as 220 Volts.

In this question we have to find energy consumed in kWh which is called as Kilo Watt Hour. We've to convert Power from watt to kilo watt.

⇒Power = 50 Watts

⇒Power = 50/1000

⇒Power = 0.05 kilo watt

And also we've to convert time from minutes to hours.

⇒Time = 20 mins

⇒Time = 20/60

⇒Time ≈ 0.34 hours

____________________________

So, energy consumed is :

$\implies \sf{Energy \: = \: Power \: \times \: Time} \\ \\ \implies \sf{Energy \: = \: 0.05 \: \times \: 0.34} \\ \\ \implies \sf{Energy \: = \: 0.017}$

$\therefore$ Energy consumed by bulb is 0.017 kWh