Required Practical 6 - Internal Resistance and EMF

What equipment is needed for rp6?

Battery/cell

Voltmeter

Ammeter

Variable resistor

Switch

Describe a method to investigate EMF and internal resistance in a cell.

1. Set up apparatus 

2. Record V with the switch open

3. Set the variable resistor to max value

4. Close switch and record V and I (open switch between readings)

5. Decrease R and repeat over the widest range possible

What graph should be plotted for rp6?

V against I

What part of the VI graph represents the EMF of the cell?

The y-intercept

What part of the VI graph represents the internal resistance of the cell?

Negative gradient

Give one safety measure that should be followed for rp6?

Avoid using high currents as wires can get hot and burn

What improvements can be made to rp6?

Only close switch while taking a reading to prevent r from changing during the experiment

Use fairly new cells as emf and r of old batteries can vary during the experiments