A heater of 220V heats a volume of water in 5 min. The same heater when connected to 110V heats the same volume of water in (minute)

Options

A. a)5
B. b)20
C. c)10
D. d)2.5

Answer

B

Explanation

Heat produced by the heater `H= V^2/R times t`
From 220 V heater produced
`H_1=(220)^2/R times 5`
From 110V heater
`H_2=(110)^2/R times t`
Now, `H_1=H_2`
`(110 times 110)/Rtimes t= (220 times 220 times 5)/R `
t=20 min