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Q68 (NDA-II/2011) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

Kilowatt-hour is the unit of

Result
Your answer: —  Â·  Correct: C
Explanation

Kilowatt-hour (kWh) is the commercial unit of electric energy [c1][c2]. While the SI unit of energy is the Joule (J), electrical energy is calculated as the product of power and time (E = P × t) [c1][t7]. One kilowatt-hour represents the energy consumed when one kilowatt (1,000 watts) of power is used for a duration of one hour [c1][t5]. This is equivalent to 3.6 million Joules (3.6 × 10^6 J) [c1][c2]. In contrast, a kilowatt (kW) is a unit of electric power, which measures the rate of energy consumption [t4][t5]. Potential difference and electric potential are measured in volts (V), representing work done per unit charge [c3]. Therefore, kWh specifically measures the total quantity of energy used over time, making it the standard unit for utility billing [t1][t2].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.8 ELECTRIC POWER > p. 191
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
  3. [3] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.2 ELECTRIC POTENTIAL AND POTENTIAL DIFFERENCE > p. 173
  4. [4] https://en.wikipedia.org/wiki/Units_of_energy
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