PDF chapter test TRY NOW

In this exercise, an activity is explained to understand linear expansion.
 
Materials Required:
  1. Bulb
  2. Dry cell
  3. Candle
  4. Cycle spoke
  5. Coin (or broad-headed nail)
  6. Two wooden blocks.
Procedure:
  • Locate one end of the cycle spoke on a wooden block, and an electric wire is attached to it.
  • As shown in the figure, put a stone over the spoke to hold it firmly in place on the wooden block.
  • The spoke should be parallel to the ground.
  • Locate the second wooden block under the free end of the spoke.
  • Wind some electric wire around the coin (or nail) and locate it on the block.
  • You may place a stone over the coin to hold it in position.
  • Attach a bulb and dry cell to the free ends of the wires attached to the coin and the spoke and form the circuit as shown in the above figure.
  • When the tip of the free end of the spoke is in contact with the coin, the circuit is closed, and the bulb lights up.
  • Verify to ensure this. If the bulb does not glow, it indicates the circuit is not closed, so check your connections properly.
  • Now slide a page of your book between the coin and spoke, and then slide it out.
  • In this way, you would get a gap between the coin and spoke equal to the thickness of the sheet of paper.
1. Does the bulb light up? If it does not, what could be the reason?
 
The bulb  because the coin and the spoke do  each other. The circuit is .
  
2. Did the bulb light up after the spoke was heated using a candle for some time?
 
When the spoke gets heated, it will be . Here,  takes place. So the spoke  the coin. The spoke is heated, which causes the circuit to be , and the bulb .
 
3. Why does the bulb go off sometime after the candle is taken away from the spoke?
 
The spoke does not get the heat once the candle is removed. The spoke is . So the spoke  the coin once again, and the bulb .
 
4. What happens to the length of the spoke when it is heated or cooled?
 
The length of the spoke is  when the spoke is heated, and the length of the spoke is  when the spoke is cooled.