Q.Distinguish between a 'movement along a demand curve' and a 'shift of the demand curve', giving one example of each.

A movement along the curve is caused by a change in the good's own price; a shift of the whole curve is caused by a change in some other factor, such as income or tastes. …

Movement along a demand curve. This happens when the price of the good itself changes, and we simply move to a different point on the same, unchanged demand curve — an upward movement (called a contraction of demand) if price rises and quantity demanded falls, or a downward movement (an extension of demand) if price falls and quantity demanded rises. Example: if the price of tea rises from Rs. 10 to Rs. 12 per 100g and, as a result, quantity demanded falls from 50 to 40 units, this is a movement along the existing demand curve for tea — the curve itself has not moved.

Shift of a demand curve. This happens when some factor other than the good's own price changes — income, the price of a related good, tastes, population, or expectations — so that a different quantity is now demanded at every price, not just at one. The entire curve moves to a new position: rightward (an increase in demand) if more is now demanded at every price, or leftward (a decrease in demand) if less is now demanded at every price. Example: if a rise in consumers' income leads them to buy more tea even at the same old price of Rs. 10, the whole demand curve for tea shifts rightward — this is not the sa …

Calling any change in quantity demanded a 'shift' — only a change caused by a non-price factor is a shift; a change caused by the go …