Question

11

An auto mechanic needs to determine the emf and internal resistance of an old battery. He performs two measurements: in the first, he applies a voltmeter to the battery's terminals and reads \( 11.6 \

Answer 1

The auto mechanic reads the emf of the old battery as E = 12.0 V and the terminal voltage as V = 10.5 V.

Ohm's law

V = ε - Ir

Substitute the given values into Ohm's law equation

10.9 V = 11.6 V - (27.5 A * r)

Simplify the equation

10.9 V = 11.6 V - 27.5 A * r

Rearrange the equation to isolate the internal resistance (r)

27.5 A * r = 11.6 V - 10.9 V

27.5 A * r = 0.7 V

Solve for r by dividing both sides of the equation by 27.5 A

r = (0.7 V) / (27.5 A)

r ≈ 0.025 Ω

the complete question is:

As an auto mechanic, you are tasked with determining the EMF (electromotive force) and internal resistance of an old battery. To obtain these measurements, you conduct the following tests: (1) You connect a voltmeter to the battery's terminals and observe a reading of 11.5 V. (2) By connecting an ammeter to the terminals, you measure a current of 10.7 A. Now, you need to calculate the EMF and internal resistance of the battery based on these measurements.