a movement on the demand curve will take place when there is
Demand curve There is movement along a demand curve when a change in price causes the quantity demanded to change.[5] It is important to distinguish between movement along a demand curve, and a shift in a demand curve. Movements along a demand curve happen only when the price of the good changes.[6] When a non-price determinant of demand changes the curve shifts. These "other variables" are part of the demand function. They are "merely lumped into intercept term of a simple linear demand function." [6] Thus a change in a non-price determinant of demand is reflected in a change in the x-intercept causing the curve to shift along the x axis.[7]
Demand PED is a measure of the sensitivity of the quantity variable, Q, to changes in the price variable, P. Elasticity answers the question of the percent by which the quantity demanded will change relative to (divided by) a given percentage change in the price. For infinitesimal changes the formula for calculating PED is the absolute value of (∂Q/∂P)×(P/Q).