Question

Kilowatt hour is the unit of

• A. Time
• B. Energy
• C. Power
• D. Impulse

Answer 1

Answer:

B. Energy

• The kilowatt-hour (kWh) is a unit of energy. It represents the amount of energy consumed or produced over a period of time.

• It is derived from the unit of power, the watt (W), and the unit of time, the hour (h).

• Specifically, 1 kWh is equal to the energy transferred or used by a device with a power of 1 kilowatt (1000 watts) operating for 1 hour.

Mathematical Representation

• Energy (in kWh) = Power (in kW) × Time (in hours)

• For example, a 100-watt light bulb operating for 10 hours consumes 1 kWh of energy (0.1 kW × 10 h = 1 kWh).

Context and Usage

• Electricity bills are typically calculated based on the consumption of energy in kilowatt-hours.

• It is a practical unit for measuring the consumption of electrical energy in homes and industries.

• While the standard SI unit for energy is the joule (J), the kilowatt-hour is more commonly used for practical electrical energy measurements due to its convenience. 1 kWh is equivalent to 3.6 million joules.

Distinction from Kilowatt (kW)

• It is crucial to distinguish kWh from the kilowatt (kW).

• Kilowatt (kW) is a unit of power, which measures the rate at which energy is transferred or used.

• Kilowatt-hour (kWh) is a unit of energy, which measures the total amount of energy consumed or produced over a duration.