RP3: Resistance

Question 1

What is the aim of this experiment?

Answer 1

• to investigate the factors that affect the resistance of an electrical component

Question 2

How would you investigate the factors that affect the resistance of an electrical component? ( Length of wire)

Answer 2

1) connect circuit; start at positive side of battery or power supply
2) connect lead from positive side of battery to positive side of ammeter
3) connect lead from negative side of ammeter to crocodile clip at zero end of ruler
4) connect a lead from other crocodile clip to negative side of battery. main loop of circuit is now complete. use this lead as a switch to disconnect battery between readings
5) connect a lead from positive side of voltmeter to the crocodile clip the ammeter is connected to
6) connect a lead from negative side of voltmeter to the other crocodile clip
7) record the length of wire between crocodile clips and record readings on ammeter and voltmeter in a suitable table
8) move the crocodile clip and record new ammeter and voltmeter readings. note that voltmeter reading may not change
9) repeat to obtain several pairs of meter readings for different lengths of wire

Question 3

How would you show your result?

Answer 3

1) plot a graph of resistance in Ω against length
2) you should be able to draw a straight line of best fit although it may not go through the origin

Question 4

List the variables

Answer 4

DV: length of wire
DV: resistance
CV: temp of wire

Question 5

What is important to do?

Answer 5

• switch off the power pack in between each reading so the wire does not get hot

Question 6

What is the conclusion of this experiment?

Answer 6

• as the length of the wire increases, so does the resistance. the relationship is directly proportional

Question 7

In reality, why might the line produced not pass through the origin?

Answer 7

• There may be a zero error
• This may be cause it is hard to attach the stationary crocodile clip exactly at the zero end of the metre ruler

Question 8

What should the graph of resistance against length look like?

Answer 8

• The two variables are directional proportional so should produce a straight line going through the origin

Question 9

Why should the wire used be thin

Answer 9

• For a given material, the thinner the wire, the higher the resistance
• Makes the recored resistance values large enough to be measure and interpreted

Question 10

Why’s should a low potential difference be used when carrying out this experiment?

Answer 10

• To prevent the current getting too high and the wire heating up

Question 11

What is the issue if the wire heats up during the experiment?

Answer 11

• Resistance of a wire will increase if the temp increases, creating an extra variable which will interfere with the results
• Temp should remain a CV

Question 12

Why does resistance increase with temp?

Answer 12

• Metal ions have more kinetic energy so vibrate more
• Causes them to collide ore frequently with current- carrying electrons providing more resistance against the flow of electrons

Question 13

List some safety precautions

Answer 13

• Avoid touching the wire since it may be very hot
• Keep potential difference vlaulves low to avoid overheating