3. A battery with a 12-V EMF has a terminal voltage of 11.4 V when it delivers 2

Question

3. A battery with a 12-V EMF has a terminal voltage of 11.4 V when it delivers 20A to the starter of a car.

a. Draw a schematic diagram of the circuit including the battery, the internal resistance of the battery, and the starter. Include a voltmeter in the circuit that measures the voltage across the starter and an ammeter that measures the total current in the circuit.

b. Calculate the internal resistance of the battery.

c. How much energy is dissipated per unit time by internal resistor. This is heat energy developed in the battery per unit time.

Please explain how u got the answer

Explanation / Answer

12 - Vr = 11.4 => Vr=0.6 V Vr is the voltage drop across the internal resistor R = Vr/I = 0.6/20 = 0.03 ohm a) since the terminal voltage is 11.4 V, the delivered emf is 11.4 V b) P = V*I =11.4*20=228 (W) c) Energy = P*t=228*3*60=41040 (joul) d) Pr = I*I*R = 20*20*0.03 = 12 (W), Pr is the power assumption at the internal resistor Heat = Pr*t=12*(3*60)=2160 (joul)

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