# Electric Current

1. Mar 4, 2009

### Kandycat

1. The problem statement, all variables and given/known data

A battery with emf, $$E$$, and internal resistance, r, is connected to a variable resistance, R, at points X and Y, as shown above on the left. Varying R changes, both the current I and the terminal voltage Vxy. The quantities I and Vxy are measured for several values of R and the data are plotted in a graph, as shown above the right.

(a) Determine the emf of the battery.

(b) Determine the internal resistance of the battery.

(c) Determine the value of the Resistance that will produce a current I of 3 amperes.

(d) Determine the maximum current that the batter can produce.

2. Relevant equations

V=IR

3. The attempt at a solution

I attempted to use Kirchhoff's loop rule. I'm not sure if I should be using it or not.

(a) $$E$$ - Ir - R = 0
$$E$$ = Ir + R

(b) r = ($$E$$ - R)/I

(c) V = IR
R = V/I = 3V/3A = 1 ohms

(d) I have no idea what to do.

Help?

2. Mar 9, 2009

### Redbelly98

Staff Emeritus
Instead of "R", that term should be "I R", the voltage across resistor R.