Required Practical 6: Internal Resistance And Emf

Question 1

Describe a method to investigate the emf and internal resistance of Cells

Answer 1

1) record the reading on the voltmeter when the switch is open
2) set the variable resistor to its maximum value
3) close switch and record value of V and I
4) decrease resistance of variable resistor and repeat to get range of values for V and I
5) open the switch between readings
6) plot a graph of V against I and draw a lien for best fit
7) the y-intercept is the emf and the internal resistance will be -1 x gradient

Question 2

Explain some safety aspects

Answer 2

Another resistor can be added in series with the other resistor so current doesn’t get too high and wire doesn’t get too hot

Question 3

How could you improve the experiment

Answer 3

• open the switch between each reading so internal resistance of battery doesn’t change
• don’t use old batteries