Kilowatt-hour(kWh) is a unit of?

Question

Examoogle · Accepted Answer

Energy

Explanation: The kilowatt-hour (kWh) is a unit of energy, defined as the amount of electrical energy consumed by a device with a power rating of one kilowatt operating continuously for one hour. It is a standard commercial unit of electrical energy used by utility companies for billing purposes.

Working Principle: Energy ($E$) is mathematically defined as the product of power ($P$) and time ($t$). Since $P = \frac{W}{t}$, then $W = P 	imes t$. When power is expressed in kilowatts ($10^3$ watts) and time in hours, the resulting product represents the total work performed or energy consumed in that duration.

Key Formulas: $E = P 	imes t$ — Fundamental relation between Energy, Power, and Time; $1 	ext{ kWh} = 3.6 	imes 10^6 	ext{ J}$ — Conversion to SI unit (Joules)

Key Points: 1 kWh is equivalent to 3.6 Megajoules (MJ).; It is the Board of Trade Unit (B.O.T.U) used in household electricity meters.; Power is the rate of energy consumption (Watts), whereas Energy is the total quantity consumed (kWh).

Advantages: Convenient scale for measuring large domestic and industrial energy consumption.; Directly correlates with standard utility billing rates.

Disadvantages: Not a fundamental SI unit; requires conversion factor to calculate mechanical work in Joules.; Can be confused with kW (power) by beginners.

Applications: Electrical utility billing (electricity bills).; Measuring battery capacity in EVs.; Energy auditing in buildings.

Additional Info: Option A (Current) is measured in Amperes (A).. Option B (Power) is measured in Watts (W) or Kilowatts (kW).. Option D (Resistance) is measured in Ohms ($\Omega$).

Answer: C is correct — Kilowatt-hour (kWh) is a unit of Energy derived from the product of power and time.

Exam Tip: Always remember: Power is the 'rate' at which you spend money, and Energy (kWh) is the 'total amount' of money spent.

Related Questions

Discussion (0)