The demand curve does not change its position here. When change in demand for a commodity is entirely due to a change in its price, it is called extension or contraction of demand. The extension or contraction in demand are movements on or along the given demand curve. It is shown in Fig. 3.


Fig. 3: Changes in Demand:
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When the price of a good is OP, demand is OQ. If the price of good falls to OP”, demand expands to OQ”. Thus extension in demand is QQ”. On the other hand, when the price of good rises to OP’ demand contracts to OQ`. Thus contraction in demand is QQ’.