According to the law of demand, what happens to the quantity demanded of a normal good when its price increases, other things remaining the same?

Introduction / Context:
The law of demand is one of the most basic principles in microeconomics. It describes the inverse relationship between the price of a good and the quantity demanded, assuming other factors such as income, tastes, and prices of related goods remain constant. This question asks what happens to the quantity demanded of a normal good when its price increases, and it directly tests understanding of the law of demand.

Given Data / Assumptions:

• The good considered is a normal good, meaning that demand for it tends to rise with income.
• All other factors affecting demand, such as income and tastes, are assumed to remain constant, which economists refer to as the ceteris paribus condition.
• Only the own price of the good is changing, and the change is an increase in price.
• The question is about the direction of change in quantity demanded, not about the mathematical size of the change.

Concept / Approach:
The law of demand states that, other things being equal, there is an inverse relationship between the price of a good and the quantity demanded. When the price of a good rises, consumers usually buy less of it because it becomes relatively more expensive. Some consumers switch to substitutes, and others cut back overall consumption. When the price falls, the good becomes relatively cheaper, and quantity demanded typically increases. Therefore, for a normal good under the usual assumptions, an increase in price leads to a decrease in quantity demanded.

Step-by-Step Solution:
Step 1: Recall the law of demand, which links price and quantity demanded inversely under constant conditions.Step 2: Focus on the situation described in the question: the price of the good is increasing.Step 3: Apply the law of demand: as price increases, consumers either reduce their purchases or shift to substitutes, so the quantity demanded decreases.Step 4: Check that other factors are held constant, so there is no change in income or preferences that would overturn this rule.Step 5: Conclude that the correct answer is that quantity demanded decreases when price increases for a normal good under ceteris paribus conditions.

Verification / Alternative check:
Demand curves in textbooks are usually drawn as downward sloping from left to right, illustrating that higher prices correspond to lower quantities demanded. Graphical analysis shows that a movement upward along a given demand curve, caused by an increase in price, leads to a point with a smaller quantity demanded. Only in rare theoretical exceptions such as Giffen goods might demand rise with price, but these are special cases and not what the law of demand describes for normal goods.

Why Other Options Are Wrong:
The statement that quantity demanded increases when price increases contradicts the law of demand and is generally false for normal goods. Saying quantity demanded remains unchanged ignores consumer sensitivity to price and is inconsistent with observed behaviour. Claiming that the effect cannot be determined in any case is incorrect because the law of demand provides a clear prediction under the given assumptions. The claim that quantity demanded becomes zero at any price increase is extreme and not supported by the general law; demand usually decreases but does not instantly fall to zero when price rises slightly.

Common Pitfalls:
Some learners confuse shifts of the demand curve with movements along the curve. A change in price causes a movement along the existing demand curve, altering quantity demanded, while changes in income or tastes shift the entire curve. Another mistake is to think that higher price always means higher revenue, forgetting that quantity demanded usually falls when price increases. Understanding the law of demand and practising with demand curves can help avoid these errors.

Final Answer:
When the price of a normal good increases, the quantity demanded decreases, other things remaining the same.