Question

two cells of emf 1 V, 2V and internal resistance of 2Ω and 1Ω are connected in series and then parallel.
What should be the external resistance in the circuit so that the current in the resistance be same in two cases ?

Answer 1

Explanation:

In series effective emf =2+1=3V

effective internal resistance =2+1=3ohm

total resistance =3+R ohm

where R=external resistance

current through the circuit=current through the external resistance =3/3+R ampere

in parallel effective emf =2V

effective resistance =2/3ohm

total resistance =2/3+R. ohm

current through the external resistance

=2/(2/3+R) Ampere

in two cases current is same

then solving two equation we get R=4ohm

As in series connection resistance is more so heat will generate more in series connection

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