The following graph shows the variation of terminal potential difference V, across a combination of three cells in series to a resistor versus the current I :
(i) Calculate the emf of each cell. (ii) For what current I, will the power dissipation of the circuit be maximum ?

Answer

`2 V`(b)`1A`

Explanation

(a) When `I = 0`, total emf = internal voltage
`:. 3 epsilon = 6.0 V or epsilon = 2.0 V`
(b) When `I = 1.0 A`
`V = (3.0)/(3) = 1.0 V` (for each cell)
If `r` is the internal resistance of a cell, then
`r = (epsilon)/(I_(max)) = (2.0)/(2.0) = 1.0 Omega`
The copper power is maximum when external resistance = internal resistance `= 3r`
`I_(max) = (3 epsilon)/(3r + 3r) = (epsilon)/(2r) = (2)/(2 xx 1) = 1A`