Question

The open-circuit voltage of a car battery is measured to be 12 V. During engine startup, the battery delivers 10 A to the starter motor, and the battery voltage drops to 11.7 V. Draw the Thévenin equivalent circuit for the battery. How much power does the battery deliver to the starter motor?

Answer 1

Answer:

- the Thevenin equivalent circuit for the battery is uploaded below

- the battery delivered 117 watts of power to the starter motor

Explanation:

Given the data in the equation

diagram of the Thevenin equivalent circuit for the battery is uploaded below.

Current I = 10 A

Voltage 1 = 12 V

voltage 2 = 11.7 v

R = (V1 - V2) / I

R = (12-11.7)/10

R = 0.3 / 10

R = 0.03Ω

Thevenin equivalent circuit

$R_{L}$ = V2 / I = 11.7 / 10

$R_{L}$ = 1.17Ω

so, power delivered to the starter motor will be;

p = (V2)² / $R_{L}$

P = ( 11.7 V )² / 1.17Ω

p =  136.89 / 1.17

p =  117 watts

Therefore, the battery delivered 117 watts of power to the starter motor