Question

An electric heater is rated 1500 W. How much energy does it use in 10 hrs.?

Answer 1

Hint : Given the power rating of the given meter, use the formula to find the energy it consumes by directly finding the product of power rating and time it runs for. 1-watt hour is equal to 3600 Joules. Convert Watt-hour to joules, which is the standard unit for energy.
 $ \Rightarrow E = 54MJ $ ( $ 1MJ = {10^6}J $ )
Thus the total energy consumed is 54 MegaJoules.

Complete step by step answer
An electric meter is rated for 1500W. Now, let us understand what you mean by power rating. The power rating of any electrical or electronics equipment is said to be the highest power input that the machine can fully function under. This means that it is the maximum power that is allowed to flow through the circuit.
Here, the maximum input power for the given heater is said to be 1500W, so when the input is given that exceeds 1500W, there are several chances that there might be several malfunctions and also chances of the shot circuit also. When the input is given less than the rated power, the operation will be slower than its normal rate or sometimes it doesn’t even start its functioning.
Now, we need to calculate the energy it consumes when the heater runs for a given time period. When the heater runs for 10 hours, the energy it consumes is given as,
 $ E = P \times t $ , Where P is the rated power of the object, and t is the time period that machine runs for.
 $ \Rightarrow E = 1500 \times 10 $
 $ \Rightarrow E = 15000Wh $
Note: 1-watt hour is equal to 3600 Joules. Convert Watt-hour to joules, which is the standard unit for energy.
 $ \Rightarrow E = 54MJ $ ( $ 1MJ = {10^6}J $ )
Thus the total energy consumed is 54 MegaJoules.

Note
Power ratings in commercial products also include average operational power and maximum operational power in its datasheet, which gives knowledge to the user about using it along with other products and also enables them to save energy accordingly.