The commercial unit of electrical energy is kilowatt hour (kWh) and 1 kW h is equal to __________.
- AOption (a)
3.6 × 108 watt second
- BOption (b)
3.6 × 106 watt second
- COption (c)
3.6 × 107 watt second
- DOption (d)
3.6 × 109 watt second
View answer & explanationHide answer & explanation
Correct answer
3.6 × 106 watt second
Why this answer is correct
The correct answer is 3.6 times 10^6 watt sec.
Key Points
- Electrical energy is the total work done by an electric current in a given time, and its commercial unit is the kilowatt-hour (kWh), often referred to as a unit in utility bills.
- The relationship between energy, power, and time is expressed by the formula Energy = Power × Time.
- To convert 1 kilowatt-hour into watt-seconds (which is equivalent to Joules), we must convert each component into its base SI units.
- 1 Kilowatt (kW) is equal to 1000 Watts (W), representing the rate of energy consumption.
- 1 Hour (h) consists of 60 minutes, and each minute has 60 seconds, totaling 3600 seconds (s).
- By multiplying these values: 1 kWh = 1000 W × 3600 s = 3,600,000 Watt-seconds.
- In scientific notation, 3,600,000 is expressed as 3.6 × 106. Therefore, 1 kWh = 3.6 × 106 watt sec.
Additional Information
- Watt (W):
- It is the SI unit of power, named after James Watt.
- One Watt is defined as the consumption of one Joule of energy per second (1 W = 1 J/s).
- Joule (J):
- The standard unit of energy in the International System of Units.
- 1 Watt-second is exactly equal to 1 Joule; thus, 1 kWh is also 3.6 × 106 Joules or 3.6 Megajoules (MJ).
- Electric Power:
- Defined as the rate at which electrical work is done or the rate at which electrical energy is transferred by an electric circuit.
- Commonly calculated using the product of Voltage (V) and Current (I), represented as P = V × I.