measuring the resistance of a wire

Question 1

how do you put wire on metre ruler?

Answer 1

tape the wire at each end of the metre ruler

Question 2

the ammeter is connected in

Answer 2

series

Question 3

the voltmeter is connected in

Answer 3

parallel

Question 4

step 2 (after general set up)

Answer 4

measure the length of the wire using a metre ruler and clip one crocodile clip at 0cm and another clip at 20cm of the wire

Question 5

step 3

Answer 5

close the switch and measure the current across the wire using an ammeter

Question 6

step 4

Answer 6

measure the potential difference using a voltmeter

Question 7

step 5

Answer 7

calculate resistance using formula (write the formula out in the exam : r= V/I)

Question 8

step 6

Answer 8

repeat at different lengths of the wire (40cm,60cm,80cm and 100cm) by moving crocodile clips

Question 9

step 7

Answer 9

repeat readings of current and p.d for each wire length, remove anomalies and calculate the mean resistance for each legnth

Question 10

what can you use to ensure the current is low?

Answer 10

a variable resistor

Question 11

why should you ensure the switch is open between readings?

Answer 11

to minimise heating of wire as it can cause burns and affect the reistance

Question 12

final step

Answer 12

plot graph with length on the x-axis and resistance on the y-axis

Question 13

independent variable

Answer 13

length of the wire

Question 14

dependent variable

Answer 14

resistance

Question 15

control variable

Answer 15

thickness of wire, material of the wire

Question 16

how would a thicker wire affect resistance?

Answer 16

the thicker the wire, the lower the resistance as it has more pathways that the electrons can go through

Question 17

the graph shows a straight line that passes through 0. What does this tell us?

Answer 17

-the resistance of the wire is directly proportional to the length

Question 18

what is a zero error and what type of error is it?

Answer 18

a zero error is when the reading on a measuring instrument should be 0.
-this is a systematic error, so cannot be reduced by carrying out repeats

Question 19

how can you deal with zero error in resistance?

Answer 19

subtract the zero error from all of our readings

Question 20

why might there be a zero error?

Answer 20

-crocodile clip is not exactly at zero, some resistance is caused by the crocodile clip and the wire

Question 21

heating effects-if temp of the wire increases, resistance increases. How can you prevent this?

Answer 21

-use a low p.d which will keep the current low, reducing any heating in the wire
-only turn on the current when taking a reading, turn off the current between readings