What is one unit of household electrical energy in J?
(A) $ 1000J $
(B) $ 3600J $
(C) $ 0.6 \times {10^3}J $
(D) $ 3.6 \times {10^6}J $

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Hint: The basic unit of electricity is Kilowatt hour (kWh). Since we need the answer in Joules we need to know what is $ 1J $ .It is equal to energy used to accelerate a body with mass of one kilogram using one Newton of force over a distance of one metre.
One Joule is equivalent to one watt per second.

Complete step by step solution
 $ 1J = 1W \times 1s $
Where, J represents Joules, W represents Watt , s is the unit for time in second.
As I mentioned earlier One unit of electrical energy is equal to
 $ \Rightarrow 1unit = 1kWh $
 $ \Rightarrow 1kWh = 1kW \times 1h $
 $ \Rightarrow 1kW = 1000w $
 $ \Rightarrow 1h = 3600s $
 $ \Rightarrow 1kWh = 1000w \times 3600s $
 $ \Rightarrow 1kWh = 3.6 \times {10^6}J $ .

Additional Information
The amount of electrical energy transferred to an appliance depends on its power and duration of the time for which the appliance is switched on. It is measured in kilowatt-hours.
 $ E = P \times t $
Where E is the energy in kWh
P is the power in kilowatt, kW
T is the time in hours, h
Ohm's law: This is one of the most important concepts of electrical energy. It states that at constant temperature, the current through the conductor is directly proportional to the potential difference across the points.
 $ V \propto I $
It can also be written as
 $ V = IR $
Where V is the potential difference
It is the current flowing through it.
R is the resistance of the conductor.

There are different types of energy like chemical, thermal, electrical, nuclear and various other forms. Regardless of type of energy it follows the law of conservation of energy which states that in a closed system, i.e, a system that is isolated from its surroundings, the total energy is conserved. Energy can neither be created nor be destroyed; it can be converted from one form to another.