Ten identical cells connected is series are needed to heated a wire of length one meter and radius 'r'by `10^(@)C` in time t. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time 't' ?

Options

A. 20
B. 30
C. 40
D. 10

Answer

A

Explanation

Since, Heat `(H) = (V^(2)/R) t` and `H= msDeltaT`
`(((10)E)^(2)t))/R = ms DeltaT`……… (i)
Now, `((ne)^(2)t)/(2R) = (2m)sDeltaT`………(ii)
`(n^(2)E^(2)t)/(2R) = (2 xx 10^(2) E^(2)t)/R rArr n = 20`