CP3 Determine EMF and Resistance of an electrical cell

Question 1

How do you setup

Answer 1

A cell, variable resistor and ammeter in series. A voltmeter in parallel around the cell.

Question 2

What is the equation we will plot

Answer 2

Vₜ = -rI + ε
y = mx + c

Question 3

What will we record

Answer 3

At least 6 pairs of current and terminal p.d.

Question 4

How will we find our results

Answer 4

Plot a graph of current on x axis and terminal p.d. on y axis. The y intercept is the emf and the gradient is -r.

Question 5

What safety measures should we take?

Answer 5

• Do not touch the variable resistor coil since it may become hot

Question 6

To stop Systematic errors?

Answer 6

• Keep temperature constant by shutting off the current between readings.

Question 7

to stop random errors?

Answer 7

• Use newer cells
• Wait for readings to stabilise before measuring them
• Take multiple readings of the same current and p.d. and average them to reduce random error further.