Determine the EMF and Internal Resistance of an Electrical Cell

Determine the EMF and Internal Resistance of an Electrical Cell

Equipment

1. Set up apparatus as shown in the diagram

2. Measure PD across the terminals, VT, using voltmeter

3. Vary current in circuit by changing value of load resistance, R using variable resistor, measure pd (V) for several values of I

4. Repeat several times and find average VT and I

5. Plot graph of VT (y axis) and I (x axis) and draw line of best fit with equation:

(1) Gradient is negative internal resistance (-r)

(2)Y intercept is EMF, ε-

1. Collect the same data as in Method 1 (Terminal PD and Current)

2. Find Power dissipated at load, P, using P = IV and read the load resistance, R, off the variable resistor

3. Plot a graph of power dissipated against load resistance (P against R):

4. Power dissipated at the load resistance is a maximum value when: Load resistance = Internal resistance