Question

the following graph shows the variation of terminal potential difference V across a combination of four cells in series to a variable 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 1

Answer:

i) EMF of each cell is 2 Volts

ii) current in the circuit for maximum power is i = 2 A

Explanation:

Part 1)

As we know that the voltage difference across the combination of cell and EMF of the combination is related as

$V = E - i r$

now in order to find out EMF of cell we can say

if i = 0 then V = E

so we have

$V = E = 8 V$ at i = 0

now EMF of combination of 4 cells is 8 V

so EMF of each cell is given as

$E = 2 V$

Part 2)

As we can see from the graph

i = 2 A V = 0

so we have

$0 = 8 - 2r$

so we have

r = 4 ohm

so total equivalent resistance of all 4 cells is 2 ohm

Now by maximum power theory we know that dissipated power will be maximum when internal resistance is same as external resistance

so R = 2 ohm and current in the circuit will be i = 2 A

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Topic : EMF of cell

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