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Q20
(NDA-II/2013)
Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism
Answer Verified
An electric heater is rated 1500 watt, electric power costs ? 2 per kilo-watt- hour then the cost of power for 10 hours running the heater is
Result
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Correct:
A
Explanation
To calculate the cost of power, we first determine the energy consumed in kilowatt-hours (kWh). The electric heater is rated at 1500 watts, which is equivalent to 1.5 kilowatts (kW) since 1000 watts equals 1 kW [1]. Energy consumption is the product of power and time [1]. For a 1.5 kW heater running for 10 hours, the energy consumed is 1.5 kW × 10 hours = 15 kWh. The commercial unit of electrical energy is the kilowatt-hour, often referred to as a 'unit' [2]. Given that the cost of electric power is ₹2 per kWh, the total cost is calculated by multiplying the energy consumed by the unit price: 15 kWh × ₹2/kWh = ₹30. Therefore, the total cost for running the heater for 10 hours is ₹30.
Sources
- [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.8 ELECTRIC POWER > p. 191
- [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
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