Water boiled in an electric kettle for 15 minutes after being switched on. Using the same main supply, should the length of the heating element be increased or decreased if the water is to boil in 10 minutes. Explain.
1 Answer
Here in both cases the same amount of heat is to be supplied, i.e.,
H1 = H2
\(\frac{V^2}{R_1}t_1=\frac{V^2}{R_2}t_2\) \(\left[\because H=I^2Rt\right]\)
Or, \(\frac{t_1}{R_1}=\frac{t_2}{R_2}\)
Since t1 is greater than t2 so, R2 is less than R1
As we know that, the resistance is directly proportional to the length, the length should be decreased of the heating element in which water boils in 10 minutes.
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