Question

An electric motor of 1.2 kW is used to do work for 15 min. Calculate the energy used by
the motor.​

Answer 1

answer will be 300 joule

E = P × T

E = 12/10 × 1000 × 15 / 60

E = 300 J

Answer 2

Given :-

◉ An electric motor of power p = 1.2 kW is used to do work for time t = 15 min.

To Find :-

◉ Energy used by the motor.

Solution :-

Since, The unit of time in power of the motor is second. (Watt = Joules per second)

Therefore, We have to first convert the given time into seconds.

⇒ t = 15 min

But, 1 min = 60 seconds

∴ t = 15 × 60

⇒ t = 900 s

We know that One watt is equal to one joule of energy consumed per second.

Here, It is given in kW which means 1.2 kW of energy will be consumed every second.

So, For 1 second ➞ Energy consumed = 1.2 kJ

∴ For 900 seconds:

⇒ Energy consumed = 1.2 × 900

⇒ Energy consumed = 1080 kJ

Hence, Energy used by the motor is 1080 kilo joules.

Some Information :-

◉ Energy consumed = Power × Time

◉ 1 Watt is defined as 1 joule of energy is consumed in one second.

• 1 kW = 1000 W
• 1 kJ = 1000 J