An electric heater operating at 220 volts boils 5 litre of water in 5 minutes. If it is used on 110 volts, it will boil the same amount of water in

Options

A. 5
B. 20
C. 10
D. 2.5

Answer

B

Explanation

W = Power `xx` time `= (V^(2) t)/( R)`
R is the same.
`therefore V^(2) t`= constant . `V_(1)^(2) t_(1) = V_(2)^(2) t_(2)`
`220^(2) xx 5 =110^(2) t_(2)`
`therefore t_(2) = 20` min.