In an electric kettle water boils in 10 m minutes. It is required to boil the boiler in 15 minutes, using same supply mains
A. Length of heating element should be decreased
B. Length of heating element should be increased
C. Length of heating element has no effect on heating if water
D. None of the above
Answer: Option A
Solution (By Examveda Team)
Power dissipated in a heating element is given by: P = V² / R, where V is the supply voltage (constant from mains) and R is the resistance of the heating element.Heat produced is proportional to power × time. To boil the same quantity of water in more time (15 minutes instead of 10 minutes), the heating element must supply less power.
Since V is constant, to reduce power, the resistance R of the element must be increased.
Resistance of a wire is proportional to its length (R ∝ L). Therefore, to increase resistance, the length of the heating element should be increased.
Final Answer: Length of heating element should be increased (Option B)
This Question Belongs to Electrical Engineering >> Current Electricity
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Comments (2)
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A. Temperature of material is decreased
B. Temperature of material is increased
C. Number of free electrons available becomes more
D. None of the above is correct
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D. Zero
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B. independent of current strength
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