When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
In the circuit shown in figure, a 12 V power supply with unknown internal resistance r is connected to a battery with unknown emf E and internal resistance 1Ω and to a resistance of 3Ω carrying a current of 2A. The current through the rechargeable battery is 1A in the direction shown. Find the unknown current i, internal resistance r and the emf E.