Question

A 3kW oven supplied with 9kJ of energy. How many seconds can it be run for? (3)

Answer 1

Answer:

10800 seconds

Explanation:

To solve this you need to use the 'power' equation:

Power = work done (energy)/time taken

In this case:

3kW = 9kJ/?

? = 3 hours

In seconds 3 hours is 10800

Answer 2

When a 3 kW oven is supplied with 9 kJ of energy then it can run for 3 seconds.

Given:

Power of oven = 3 kW

Energy supplied = 9 kJ

To Find:

Running time of the oven

Solution:

→ Power is the rate of doing work. This means Power is equal to the total work done divided by the total time taken.

• Power of Oven (P) = 3 kW = 3000 W (S.I. unit)

• Energy Supplied (E) = 9 kJ = 9000 J (S.I. unit)

This Energy(E) supplied to the oven will be used by oven to convert it into Heat Energy. This Heat Energy generated by the oven can be treated as the Work Done by the oven.

                                 $Power(P)= \frac{EnergySupplied(E)}{Total Time(T)}\\\\Total Time(T) = \frac{EnergySupplied(E)}{Power(P)} \\\\T = \frac{E}{P}= \frac{9000}{3000} =3 s$

                                 ∴ Time = 3 seconds

Hence, when a 3 kW oven is supplied with 9 kJ of energy then it can run for 3 seconds.

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