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Q11
(NDA-II/2022)
Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism
The commercial unit of electrical energy is kilowatt-hour (kWh), which is eal to
Result
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Correct:
A
Explanation
The kilowatt-hour (kWh) is the commercial unit of electrical energy, often referred to as a 'unit' in domestic billing [1][2]. To determine its value in joules, we multiply power by time. One kilowatt equals 1,000 watts, and one hour equals 3,600 seconds [1]. Since energy is the product of power (in watts) and time (in seconds), 1 kWh is calculated as 1,000 W!! 3,600 s, which equals 3,600,000 joules. In scientific notation, this value is expressed as 3.6!! 10^6 J [1][2]. This conversion is essential because while the joule is the SI unit of energy, it is too small for practical commercial measurement, necessitating the use of the larger kilowatt-hour for electricity consumption.
Sources
- [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
- [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.8 ELECTRIC POWER > p. 191
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