There is no supply curve in monopoly-Explain.

For profit maximization, competitive and monopoly firms are same. But, still there is a difference between the two.

For a competitive firm:- P=MR=MC  

For a monopoly firm:-  P>MR=MC 

So, you see, MR & MC are equivalent for both type of firms but the relationship between Price, MC & MR differ for both.

For a competitive firm: Price = Marginal Revenue = Average Revenue = Demand = Marginal Cost.

So, you see, MR & MC are equivalent for both type of firms but the relationship between Price, MC & MR differ for both.

For a competitive firm: Price = Marginal Revenue = Average Revenue = Demand = Marginal Cost.

For a monopoly firm: Price > Marginal Revenue = Marginal Cost.

Here for a monopoly, in panel (b) the demand curve is shifted up from D1 to D2. The new Marginal Revenue curve, MR2 , intersects the Marginal Cost curve at a larger quantity Q2. But the shift in the demand curve is in a way that the price charged is the same. Shifts in demand normally cause changes in both quantity and price.

If we study the monopolist demand curve, we observed that monopoly market using the market demand curve and the firm's cost curves. However, we don't find any supply curve.

So, what exactly happened to the supply curve? Well, like any other firm, monopolist also  make decision about what quantity to supply but it doesn't have a supply curve. If we go definition, then supply curve tells us that firms choose to supply at any given price. And, it makes sense for competitive firms as they are price takers. But, a monopolist is a price-maker. So, there is no meaning to know at what price firm would sell what quantity because monopolist firm sets the price at the same time it chooses the quantity to supply.

However, the monopolist decision about what quantity to supply is difficult to separate from the demand curve it gets. Because shape of demand curve determines the shape of MR curve which determines the profit maximization of the monopolist.

That's why, monopolist has a demand curve but not a supply curve.