Paper 3: Required practical 4 - Determination of Young's Modulus

Question 1

How can the cross sectional area of a thin wire be measured?

Answer 1

• Measure the diameter
• In several places along the wire at several angles with a micrometer
• The average diameter can be used the calculate the mean cross-sectional area

Question 2

What safety precaution should be taken when stretching thin wires?

Answer 2

Saftey goggles should be worn since the wire may snap when under a tensile load and could cause an eye injury

Question 3

Why should the temperature of the surroundings be kept constant when carrying out this experiment?

Answer 3

Metals undergo thermal expansion when there is a temperature increse, and this would slightly change the dimensions of the wire

Question 4

Why should a pre-stress be applied to the wire when setting up this experiment?

Answer 4

So all the kinks in the wire are removed and the wire is taught, before measurements are taken

Question 5

How can the extension of the wire be measured?

Answer 5

• Marker - small piece of tape added to the wire
• A ruler placed underneath the wire, allowing the movement of the marker to be measured

Question 6

Why is it important to choose the right diameter of wire in obtaining successful results?

Answer 6

• If the wire is too thick, the extension will be too small to measure
• If the wire is too thin, the wire may begin to plastically deform before a good range of results have been obtained

Question 7

Why should you choose the correct length of wire in this experiment?

Answer 7

The length needs to be sufficiently long enough for the extensions to be easily measureable

Question 8

How would you fix the wire in place when carrying out this experiment?

Answer 8

Clamped tightly between 2 blocks of wood at one end - blocks then clamped to the bench

Question 9

What 2 pieces of equipment should you use to measure the extension?

Answer 9

Set square and extension