Linear Expansion Take a bulb, dry cell, candle, cycle spoke, coin (or broad – headed nail) and two wooden blocks.Place one end of the cycle spoke on a wooden block and connect an electric wire to it. Put a stone over the spoke) to hold it firmly in place on the wooden block, as shown in Figure . The spoke should be parallel to the ground. Place the second wooden block under the free end of the spoke. Wrap some electric wire around the coin (or nail) and place it on the block. You may put a stone over the coin to hold it in place.Connect a bulb and dry cell to the free ends of the wires connected to the coin and the spoke and make the circuit shown in the figure.When the tip of the free end of the spoke touches the coin, the circuit is completed and the bulb lights up. Check to ensure this. If the bulb does not light up, it means the circuit is not complete, so check your connections properly. (Note: We will learn about electric circuit elaborately in electricity lesson.) Now slide a page of your book between the coin and spoke and then slide it out. That 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? ___________________ You saw that the bulb does not light up when the spoke does not touch the coin. Now light the candle and heat the spoke with it. 2. Did the bulb light up after the spoke was heated for some time? 3. If it did, then explain how the spoke touched the coin after it was heated. 4. Why does the bulb go off some time after the candle is taken away from the spoke? 5. What happens to the length of the spoke when it is heated or cooled?