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## Homework Statement

A battery with emf [tex]\epsilon[/tex] and internal resistance r is connected to a variable resistance R at points X and Y. Varying R changes both the current I and the terminal voltage V

_{xy}. The quantities I and V

_{xy}are measured for several values of R and the data are plotted in a graph, as shown above on the right.

a. Determine the emf [tex]\epsilon[/tex] of the battery.

b. Determine the internal resistance r of the battery.

c. Determine the value of the resistance R that will produce a current I of 3 amperes.

d. Determine the maximum current that the battery can produce.

e. The current and voltage measurements were made with an ammeter and a voltmeter. On the diagram below, show a proper circuit for performing these measurements. Use A to represent the ammeter and V to represent the voltmeter.

**Diagram is #4 from this link: http://mrmaloney.com/mr_maloney/ap/past-AP-tests/BII_91.pdf

## Homework Equations

[tex]\epsilon[/tex] = IR + Ir

[tex]\Delta[/tex]V = IR

## The Attempt at a Solution

a) I know a battery is a constant source of emf.

[tex]\epsilon[/tex] = IR + Ir

[tex]\epsilon[/tex] = [tex]\Delta[/tex]V + Ir

From the diagram:

[tex]\epsilon[/tex] = (4-2) + Ir

Help! What values do I use?