physics - investigating how resistance depends on the length of wire

Question 1

what are the steps of the practical?

Answer 1

• set up a circuit
• attach resistance wire to a metre rule
• move the crocodile clips along the wire in increments, taking measurements for voltage and current each time
• calculate the resistance for each length

Question 2

what two types of meters are needed in the circuit, and how should they be connected?

Answer 2

• voltmeter ~ connected in parallel
• ammeter ~ connected in series

Question 3

how to calculate resistance using the readings?

Answer 3

R = V/I

Question 4

what should the graph of resistance against length look like?

Answer 4

a straight line ~ the variables are directly proportional

Question 5

why might the line on the graph not pass through the origin?

Answer 5

there may be a zero error ~ this could occur as it is hard to attach the crocodile clip exactly at the zero end of the metre rule

Question 6

why should the wire used be thin?

Answer 6

• the thinner the wire, the higher the resistance
• this makes the recorded resistance values large enough to be recorded and interpreted

Question 7

why should a low potential difference be used when carrying out this experiment?

Answer 7

to prevent the current getting too high and the wire heating up

Question 8

why is it an issue that the wire heats up?

Answer 8

resistance of the wire will increase if the temperature increases, creating an extra variable which will interfere with results. Temperature should remain a control variable

Question 9

why does resistance increase with temperature?

Answer 9

the metal ions have more kinetic energy, so they vibrate more. This causes them to collide more frequently with current carrying electrons, providing more resistance against the flow of electrons

Question 10

what safety precautions should be followed?

Answer 10

• avoid touching the wire as it may become very hot
• keep potential difference values low to prevent overheating