Electrical Power Dissipation
An electric heater rated to carry 5 amperes operates across a 220 volt mains supply in a kitchen, so how much power does it consume?
Select the correct option:
Solution
1100 W
Electrical power delivered to a resistive device is the product of the voltage across it and the current through it, written as P=VI, a formula presented in NCERT Class 12, Chapter 3 (Current Electricity). Substituting the operating values, P=220×5=1100 W. This is the rate at which electrical energy is converted into heat in the heating element. The option 44 W wrongly divides the voltage by the current, which would give resistance-like units, not power. The option 225 W simply adds voltage and current, an operation with no physical meaning since they carry different units. The option 215 W subtracts current from voltage, which is equally meaningless dimensionally. A magnitude check confirms plausibility: a kitchen heater drawing several amperes at mains voltage is expected to consume on the order of a kilowatt, and 1100 W is a realistic rating, while watts as volts times amperes is dimensionally correct.
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About This Question
- Subject
- physics
- Chapter
- current electricity
- Topic
- electrical power dissipation
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
1100 W
Electrical power delivered to a resistive device is the product of the voltage across it and the current through it, written as P=VI, a formula presented in NCERT Class 12, Chapter 3 (Current Electricity). Substituting the operating values, P=220×5=1100 W. This is the rate at which electrical energy is converted into heat in the heating element. The option 44 W wrongly divides the voltage by the current, which would give resistance-like units, not power. The option 225 W simply adds voltage and current, an operation with no physical meaning since they carry different units. The option 215 W subtracts current from voltage, which is equally meaningless dimensionally. A magnitude check confirms plausibility: a kitchen heater drawing several amperes at mains voltage is expected to consume on the order of a kilowatt, and 1100 W is a realistic rating, while watts as volts times amperes is dimensionally correct.
This easy difficulty physics question is from the chapter current electricity, covering the topic of electrical power dissipation. It appeared in the 2025 exam.
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