To investigate how the length of the wire made of lead changes with time as temperature and the load which it supports are changed.
Diagram: Draw a long box. The lead wire hangs from the ceiling support. A load is used to keep the wire taut. A heater (box) is placed at the bottom and connected to power supply. A ruler with with vernier scale is placed along side the wire to measure length. A thermostat is placed in in series with heater to maintain constant temperature. A thermometer is placed in the box with holder.
Procedure:
1.Set up the lead wire in the box as shown above.
2.Turn on the heater and record the temperature of the air in the box using a thermometer when it is steady. Keep the temperature constant with the adjustment made at the thermostat with heater.
3. Place slotted masses at the end of the wire and record the total mass of the slotted masses.
4. Measure the length of the wire using a ruler with verneir scale attached . Use a stopwatch to measure time and record the length regularly with time.
5. Obtain 8 sets of length and time keeping the load and temperature constant .
6. Repeat steps 2 to 5 by varying the temperature of the air around the wire in the box.
7. Repeat steps 2 to 5 by varying the load used to stretch the wire.
Reliability :
1. Use a long wire so that the extension is significantly large.
2 Measure the diameter of the wire at several places to check of uniformity.
3 measure the extension over a long period of time.
4 Use a kink free wire.
Precauation:
1 Wear goggles when handling the wire to protect the eye if the wire breaks suddenly.
2. Use gloves to handle the apparatus in the box as it is hot.
