Dangerous Ideas! Beware!

While I enjoyed this week's lessons on drawing of demand and supply graphs so far. I have come to notice that students have some dangerous ideas lurking in their minds.

Dangerous idea #1: An increase in Demand, ceteris paribus, will cause Supply to
increase.

This is absolutely something we want to avoid. What you guys actually meant is that an increase in demand will cause quantity supplied to increase. Take a look at the following diagrams.


Fig 1 shows that when demand curve shifts from D to D1, price increases from P1 to P2. Upon seeing a higher price, producers will have more incentive to increase production. This leads to an increase in quantity (supplied) from Q1 to Q2. Now, take a close look at Fig 2. It is actually the same supply seen in Fig1 without the demand curves.

Can you see that there as price increases from P1 to P2, there is an increase in quantity supplied from Q1 to Q2?

Henceforth, once again, an increase in demand, ceteris paribus, will cause quantity supplied to increase.

Dangerous Idea #2: An increase in supply, ceteris paribus, will cause demand to increase.

This dangerous idea is similar to the above. Therefore, the explanation to debunk such dangerous idea is the same as discussed above. (Please try out the explanation yourself). The correct understanding should be an increase in supply, ceteris paribus, will cause quantity demanded to increase.