CP2 Determine the Electrical Resistivity of a Material

Question 1

What are the variables

Answer 1

Independent: Length of wire measured,
Dependent: The current through the wire
Control variables: Voltage across the wire, the wire’s material

Question 2

What measurements should you take first

Answer 2

• Measure the diameter of the wire with a micrometre at least 3 times and repeat and average.

Question 3

How do you take measurements

Answer 3

Move the probe along the wire in regular intervals and take readings of the current and pd.

Question 4

What equation should be used

Answer 4

R = p/A * l
y = mx

Question 5

Safety?

Answer 5

Do not touch wire

Question 6

Systematic errors?

Answer 6

• Make sure that the probe is on 0 at the start

Question 7

Random errors

Answer 7

• Only allow small currents to go through the wire since resistivity is dependent on temperature and current causes the wire’s temperature to increase
• Switch of current between readings to prevent temperature rise
• Avoid pressure on the wire, which might change surface area