Market Equilibrium Class 11: Updated NCERT Solutions & Important Questions [2026-27]

Market equilibrium is a state in a market where the plans of all buyers and sellers match. At this point, the quantity of a good that buyers are willing and able to purchase (quantity demanded) is exactly equal to the quantity that sellers are willing and able to offer for sale (quantity supplied).

This point of balance occurs at the intersection of the demand curve and the supply curve.

• The price at this intersection is called the equilibrium price.
• The quantity at this intersection is called the equilibrium quantity.

In an equilibrium state, the market is stable, and there's no pressure for the price to go up or down. Any buyer who wants to buy at the equilibrium price can find a seller, and any seller who wants to sell at that price can find a buyer.

We say there is excess demand for a commodity when, at a given price, the quantity demanded is greater than the quantity supplied. This situation is also known as a market shortage.

This typically happens when the prevailing market price is below the equilibrium price.

• Why it happens: At a lower price, consumers are willing to buy more (law of demand), while producers are willing to supply less (law of supply). This mismatch creates a shortage.
• Effect: When there is excess demand, buyers will compete with each other to get the limited goods. This competition puts upward pressure on the price. As the price rises, demand contracts and supply expands, moving the market back towards equilibrium.

We say there is excess supply for a commodity when, at a given price, the quantity supplied is greater than the quantity demanded. This situation is also known as a market surplus.

This typically happens when the prevailing market price is above the equilibrium price.

• Why it happens: At a higher price, producers are incentivized to supply more, but consumers are willing to buy less. This creates a surplus of unsold goods.
• Effect: When there is excess supply, sellers will find their stocks piling up. To clear their inventory, they will start lowering the price. This downward pressure on the price causes demand to expand and supply to contract, moving the market back towards equilibrium.

An increase in the price of inputs (like raw materials, labour costs, etc.) makes production more expensive. This leads to a decrease in supply. The supply curve will shift to the left.

Assuming demand remains unchanged, the effects will be:

1. New Equilibrium: The new supply curve (S') will intersect the original demand curve (D) at a new, higher point.
2. Effect on Equilibrium Price: The equilibrium price will increase.
3. Effect on Equilibrium Quantity: The equilibrium quantity will decrease.

In simple terms, since it's costlier to produce the good, less of it is supplied at every price. With the same level of demand, this scarcity pushes the price up, and fewer goods are ultimately bought and sold.

An increase in the price of a substitute good (e.g., if the price of coffee increases, what happens to the tea market?) makes the commodity in question relatively cheaper and more attractive. This leads to an increase in demand for the commodity. The demand curve will shift to the right.

Assuming supply remains unchanged, the effects will be:

1. New Equilibrium: The new demand curve (D') will intersect the original supply curve (S) at a new, higher point.
2. Effect on Equilibrium Price: The equilibrium price will increase.
3. Effect on Equilibrium Quantity: The equilibrium quantity will also increase.

In simple terms, more people want to buy the good now. This increased competition among buyers pushes the price up, and producers respond by supplying more at this higher price.

In a perfectly competitive market with a fixed number of firms, the price is determined by the collective forces of market demand and market supply. No single buyer or seller can influence the price; they are all "price takers."

The determination process is as follows:

1. Market Demand: This is the sum of the quantities demanded by all individual consumers at various prices. It is represented by a downward-sloping demand curve.
2. Market Supply: This is the sum of the quantities supplied by all individual firms at various prices. It is represented by an upward-sloping supply curve.
3. Equilibrium: The market price is determined at the point where the market demand curve intersects the market supply curve. This is the equilibrium price.
   • If the price is above equilibrium, there is excess supply, which pushes the price down.
   • If the price is below equilibrium, there is excess demand, which pushes the price up.

This "invisible hand" of market forces ensures that the price automatically adjusts to the level where the quantity demanded equals the quantity supplied, achieving market equilibrium.

This is a classic question from the CBSE Class 11 Micro Economics Chapter 5 board exam perspective.

Given Equations:

Demand Equation: \(Q_d = 100 – P\)

Supply Equation: \(Q_s = 70 + 2P\)

Step 1: Understand the equilibrium condition
At market equilibrium, the quantity demanded must equal the quantity supplied.
Therefore, \(Q_d = Q_s\)

Step 2: Set the equations equal to each other
$$100 – P = 70 + 2P$$

Step 3: Solve for the equilibrium price (P)
Move the 'P' terms to one side and the constant numbers to the other.
$$100 - 70 = 2P + P$$ $$30 = 3P$$ $$P = \frac{30}{3}$$ $$P = 10$$ So, the equilibrium price is ₹10.

Step 4: Solve for the equilibrium quantity (Q)
Substitute the equilibrium price (P=10) back into either the demand or the supply equation. Let's use both to verify.
Using the demand equation: \(Q_d = 100 – P = 100 – 10 = \mathbf{90}\)
Using the supply equation: \(Q_s = 70 + 2P = 70 + 2(10) = 70 + 20 = \mathbf{90}\)
Since both calculations give the same result, we can be confident in our answer.

1. Price Ceiling

• Definition: A price ceiling is a government-imposed maximum price that can be charged for a good or service. It is set below the equilibrium price to make essential goods affordable for the poorer sections of society.
• Example: Rent control on apartments, price caps on essential medicines.
• Implications: When a price ceiling is effective (i.e., set below equilibrium), it leads to excess demand or a shortage of the commodity. This can lead to problems like black marketing, rationing, and long queues.

2. Price Floor

• Definition: A price floor is a government-imposed minimum price that must be paid for a good or service. It is set above the equilibrium price to protect the income of producers.
• Example: Minimum Support Price (MSP) for agricultural crops in India, minimum wage laws for labourers.
• Implications: When a price floor is effective (i.e., set above equilibrium), it leads to excess supply or a surplus of the commodity. The government often has to buy this surplus stock to maintain the price floor.

Movement along the demand curve (change in quantity demanded) occurs due to a change in the good's own price. An upward movement means a contraction in demand (due to a price rise), and a downward movement means an expansion in demand (due to a price fall).

Shift in the demand curve (change in demand) occurs due to changes in factors *other than* the good's own price, like income, tastes, price of related goods, etc. A rightward shift signifies an increase in demand, and a leftward shift signifies a decrease in demand.

An improvement in technology lowers the cost of production. This encourages producers to supply more at every price, leading to an increase in supply. The supply curve shifts to the right.

Effect:

• Equilibrium price will decrease.
• Equilibrium quantity will increase.

The statement "Equilibrium is a state of rest" means that once a market reaches its equilibrium point (where Qd = Qs), there is no internal tendency for the price or quantity to change. The market is balanced. The upward pressure on price from buyers is perfectly offset by the downward pressure from sellers. It will remain in this state of "rest" unless disturbed by an external factor, such as a change in consumer income (shifting demand) or a change in input costs (shifting supply).

Excess supply occurs when the market price is above the equilibrium price. The chain of effects is as follows:

1. Initial Situation: At price P1 (where P1 > P*), Quantity Supplied (Qs) is greater than Quantity Demanded (Qd). This results in a surplus.
2. Competition among Sellers: Firms are unable to sell all their output. Their inventories start piling up. To clear their stock and attract customers, sellers start competing by lowering their prices.
3. Price Reduction: This competition puts downward pressure on the market price.
4. Response of Buyers: As the price falls, consumers are willing to buy more. There is an expansion of demand (a downward movement along the demand curve).
5. Response of Sellers: As the price falls, the incentive for producers to supply the good diminishes. There is a contraction of supply (a downward movement along the supply curve).
6. New Equilibrium: This process of falling prices continues until the market reaches the original equilibrium point 'E', where Qd again equals Qs. The surplus is eliminated, and the market is back in balance.

When both demand and supply increase (both curves shift to the right), the effect on the equilibrium quantity is certain: it will increase.

However, the effect on the equilibrium price is uncertain and depends on the relative magnitude of the shifts.

• Case 1: Increase in Demand > Increase in Supply
  • The rightward shift of the demand curve is larger than the rightward shift of the supply curve.
  • Result: Equilibrium price increases, and equilibrium quantity increases.
• Case 2: Increase in Demand < Increase in Supply
  • The rightward shift of the supply curve is larger than the rightward shift of the demand curve.
  • Result: Equilibrium price decreases, and equilibrium quantity increases.
• Case 3: Increase in Demand = Increase in Supply
  • Both curves shift to the right by the same proportion.
  • Result: Equilibrium price remains unchanged, and equilibrium quantity increases.

1. What was the initial effect on the market for face masks due to the pandemic? (1 Mark)
   Answer: There was a massive rightward shift in the demand curve for face masks, leading to a sharp increase in both equilibrium price and quantity.
2. What was the effect of new firms entering the market? (1 Mark)
   Answer: The entry of new firms caused an increase in supply, leading to a rightward shift of the supply curve.
3. The government's cap of ₹10 per mask is an example of what? (1 Mark)
   Answer: This is an example of a Price Ceiling.
4. If the equilibrium price (without government intervention) was ₹25, what would be the likely consequence of the ₹10 price cap? (1 Mark)
   Answer: Since the price ceiling (₹10) is below the equilibrium price (₹25), it would lead to excess demand or a shortage of masks.