An ideal voltmeter is connected to the terminals of a real battery and is kept t

Question

An ideal voltmeter is connected to the terminals of a real battery and is kept there for the duration of the following experiments. (The voltmeter reads a positive value if its “+” terminal is at higher potential than its “–” terminal, and a negative value if the opposite is true.) Two separate measurements are made using the voltmeter, each with different connections in the hidden portion of the left branch.

In Experiment 1, there is an open connection in the hidden portion; that means there is a gap in the wire, so there is no physical connection on that branch. The voltmeter reads +V1.

In Experiment 2, there is a single resistor with resistance R0 in the hidden portion. The voltmeter reads +V2.

A. [2 pts] Determine the EMF of the battery in terms of some or all of the given variables (V1, V2, and/orR0). Show your work very neatly; convince the grader you understand the relevant physics.

B. [3 pts] Determine the internal resistance of the battery in terms of some or all of the given variables (V1,V2, and/or R0). Show your work very neatly; convince the grader you understand the relevant physics.

Explanation / Answer

V1= e ( where e = emf of the battery)

V2= e + IR0 (where R0 is the resistance and I is the current through that resistor)

e= V2- IR0

V2= Ir + IR0 ( where r is the internal resistance of the battery)

r= ( V2 - IR0)/ I

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