The Price at which the Quantity Demanded is equal to the Quantity Supplied, is known as Equilibrium Price. At this Price there is neither Excess Demand Nor Excess Supply. Therefore there is No Tendency, for the Price to Change. Equilibrium Price under Perfect Competition Market is determined by the Comparative Power of Market Demand and Market Supply. Because in Perfect Competition Market there are large number of Buyers and Sellers who exist in Market. Therefore Share of a Single Seller or a Single Buyer is very minute fraction of Total Supply and Total Demand of the Market. Therefore an Individual Seller or Buyer is unable to affect the Market Supply , Market Demand and Market Prices.
