When switch S in the figure ( Figure 1 ) is open, the voltmeter V of the battery

Question

When switch S in the figure (Figure 1) is open, the voltmeter V of the battery reads 3.10V . When the switch is closed, the voltmeter reading drops to2.97V , and the ammeter A reads 1.69A . Assume that the two meters are ideal, so they don't affect the circuit.

When switch S in the figure (Figure 1) is open, the voltmeter V of the battery reads 3.10V . When the switch is closed, the voltmeter reading drops to2.97V , and the ammeter A reads 1.69A . Assume that the two meters are ideal, so they don't affect the circuit. Find the emf. Find the internal resistance of the battery. Find the circuit resistance R.

Explanation / Answer

A)

Since the switch is open no current goes through the lower branch. The voltmeter is ideal, so no current runs through the meter, thus current through internal resister is zero. This means there is no voltage loss across the internal resistor:

V1=3.10V

so E=3.10V

B) Find the internal resistance of the battery

V2=2.97V

I=1.69A

V2=E-rI

so r=(E-V2)/I

r=0.0769 ohm

C)

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