to measure the resistivity of the material of a wire

Question 1

describe how the student measured the resistance of the wire.

Answer 1

an ohmmeter is used to measure the resistance, making sure to account for the resistance of the probes themselves first

Question 2

describe the procedure used in measuring the length of the sample of wire.

Answer 2

the wire is straightened out along the length of a metre stick, making sure it is free from kinks, and a measurement is taken from the edge of each of the crocodile clips connected to the ohmmeter using a metre stick

Question 3

how do you calculate the cross-sectional area of the wire.

Answer 3

a micrometer screw gauge is gently clamped at several points along the length of the wire. Accounting for the zero error, an average of these values is taken as the diameter of the wire. The cross sectional area is given by A=A= pie r squared

Question 4

what instrument did the student use to measure the diameter of the wire?

Answer 4

a micrometer screw gauge with a sensitive vernier scale

Question 5

why did the student measure the diameter of the wire at different places?

Answer 5

to ensure an accurate value of the diameter, as the wire may have slight inconsistencies in cross sectional area from manufacturing

Question 6

give two precautions that the student took when measuring the length of the wire

Answer 6

parallax error when measuring the length

account for zero error on the micrometer screw gauge when measuring diameter

Question 7

the experiment was repeated on a warmer day. what effect did this have on the measurements?

Answer 7

increased temperature would increase the resistance of the wire. changes in temperature may also cause expansion of the wire, changing the length/cross sectional area slightly