Question

A battery of internal resistance 3 ohm is connected to 20 ohm resistor and potential difference across the resistor is 10ohm.

If another resistor of 30 ohm is
connected in series with the first resistor and battery is again connected to the combination,

calculate the emf and terminal potential difference across the
combination.

Please answer fast​

Answer 1

Let the emf of the battery be E.

Internal resistance of battery r=3Ω.

Voltage across the resistor 20Ω is 10 volts.

Voltage across resistor 20Ω V=

R+r

R

E

∴ 10=

20+3

20

E

⟹ E=11.5 volts

Now another resistor 30Ω is connected in series with battery and previous resistor.

Total resistance of the circuit R

eq

=30+20+3=53Ω

Current flowing through the circuit I=

R

eq

E

∴ I=

53

11.5

=0.22 A

Thus terminal potential difference across the combination V

′

=I(20+30)

∴ V

′

=0.22×50=11 volts