Important Questions Class 12 Micro Economics Chapter 2: Theory of Consumer Behaviour

Theory of Consumer Behaviour explains how a rational consumer chooses the best affordable bundle of goods from available options.
Important Questions Class 12 Micro Economics Chapter 2 help students revise utility, budget line, consumer equilibrium, demand and elasticity.

Theory of Consumer Behaviour is a concept-heavy Class 12 Microeconomics chapter where definitions alone are not enough. Students must understand why a consumer buys more at a lower price, why marginal utility falls, why indifference curves slope downward, and how budget limits affect choice. The chapter uses simple examples like bananas and mangoes to explain larger ideas such as utility, preferences, budget set, optimum bundle, normal goods, inferior goods, substitutes, complements, market demand and price elasticity of demand. For the 2026-27 exam, this chapter is important for MCQs, assertion-reason questions, diagram-based answers, numerical elasticity questions and case-based consumer-choice questions.

Key Takeaways

• Utility: Utility means the want-satisfying capacity of a commodity.
• Marginal Utility: Marginal utility is the change in total utility after consuming one more unit.
• Budget Line: A budget line shows all bundles that cost exactly equal to the consumer’s income.
• Consumer Optimum: A rational consumer chooses the most preferred affordable bundle.

Important Questions Class 12 Micro Economics Chapter 2 Structure 2026-27

Section A: MCQs from Important Questions Class 12 Micro Economics Chapter 2

Theory of Consumer Behaviour MCQs usually test terms, formulas, curve shapes and cause-effect logic. Focus on the condition mentioned in the question before selecting the answer.

Q1. Utility means:

1. Market price of a commodity
   b. Want-satisfying capacity of a commodity
   c. Cost of producing a commodity
   d. Income of a consumer

Answer: b. Want-satisfying capacity of a commodity

Utility shows the satisfaction a consumer gets from consuming a good.

Q2. Utility is:

1. Always objective
   b. Always same for all consumers
   c. Subjective
   d. Independent of time and place

Answer: c. Subjective

Different consumers may get different utility from the same commodity.

Q3. Cardinal utility analysis assumes that utility can be:

1. Ranked only
   b. Measured in numbers
   c. Ignored completely
   d. Shown only through budget line

Answer: b. Measured in numbers

Cardinal utility analysis expresses utility in numerical units.

Q4. Ordinal utility analysis assumes that utility can be:

1. Ranked in order of preference
   b. Measured exactly in units
   c. Calculated only by price
   d. Measured only by income

Answer: a. Ranked in order of preference

Ordinal utility analysis ranks bundles as more preferred, less preferred or indifferent.

Q5. Total utility is:

1. Satisfaction from one extra unit
   b. Total satisfaction from consuming a given quantity
   c. Price paid for a good
   d. Income spent on two goods

Answer: b. Total satisfaction from consuming a given quantity

Total utility increases as long as marginal utility is positive.

Q6. Marginal utility is calculated as:

1. MU(n) = TU(n) - TU(n-1)
   b. MU(n) = TU(n) + TU(n-1)
   c. MU(n) = Price / Quantity
   d. MU(n) = Income / Price

Answer: a. MU(n) = TU(n) - TU(n-1)

Marginal utility shows the change in total utility from one additional unit.

Q7. When marginal utility is zero, total utility is:

1. Minimum
   b. Maximum or constant at that point
   c. Negative always
   d. Equal to price always

Answer: b. Maximum or constant at that point

When MU becomes zero, TU stops increasing.

Q8. The law of diminishing marginal utility states that:

1. MU rises with each extra unit
   b. MU falls as consumption increases
   c. TU always falls from the first unit
   d. Price always rises with income

Answer: b. MU falls as consumption increases

The desire for extra units becomes weaker after more consumption.

Q9. An indifference curve shows:

1. Bundles giving equal satisfaction
   b. Bundles with equal prices only
   c. Bundles outside the budget set only
   d. Bundles with zero utility

Answer: a. Bundles giving equal satisfaction

A consumer is indifferent among all bundles on the same indifference curve.

Q10. An indifference curve generally slopes:

1. Upward from left to right
   b. Downward from left to right
   c. Vertically only
   d. Horizontally only

Answer: b. Downward from left to right

More of one good requires less of another to keep satisfaction constant.

Q11. Marginal rate of substitution means:

1. Rate at which a consumer is willing to substitute one good for another
   b. Rate at which income changes
   c. Rate at which price rises
   d. Rate at which tax changes

Answer: a. Rate at which a consumer is willing to substitute one good for another

MRS shows willingness to give up one good for another.

Q12. The usual shape of an indifference curve is:

1. Concave to origin
   b. Convex to origin
   c. Vertical straight line
   d. Horizontal straight line

Answer: b. Convex to origin

Diminishing MRS makes the indifference curve convex to the origin.

Q13. Two indifference curves:

1. Always intersect
   b. Never intersect
   c. Always touch the budget line
   d. Always have same slope

Answer: b. Never intersect

Intersection would create contradictory satisfaction rankings.

Q14. Budget line shows:

1. All bundles that cost exactly equal to income
   b. Only unaffordable bundles
   c. Only free goods
   d. Only inferior goods

Answer: a. All bundles that cost exactly equal to income

Bundles below the budget line cost less than income.

Q15. The budget constraint is:

1. p1x1 + p2x2 ≤ M
   b. p1x1 - p2x2 = M
   c. x1 + x2 = p1
   d. M = p1 - p2

Answer: a. p1x1 + p2x2 ≤ M

It shows all bundles affordable at given prices and income.

Q16. The slope of the budget line is:

1. -p1 / p2
   b. p1 + p2
   c. M / p1
   d. M / p2

Answer: a. -p1 / p2

The slope shows the market rate of substitution between two goods.

Q17. Consumer equilibrium occurs where:

1. Budget line is tangent to an indifference curve
   b. Two budget lines intersect always
   c. Income is zero
   d. Marginal utility is always negative

Answer: a. Budget line is tangent to an indifference curve

At this point, the consumer chooses the best affordable bundle.

Q18. The law of demand states that, other things being equal:

1. Price and demand move in the same direction
   b. Price and demand move in opposite directions
   c. Income and demand are always equal
   d. Demand is independent of price

Answer: b. Price and demand move in opposite directions

When price rises, quantity demanded usually falls.

Q19. Assertion: Demand curve generally slopes downward.

Reason: Lower price increases quantity demanded, other things being equal.

1. Assertion and Reason are true, and Reason explains Assertion
   b. Assertion and Reason are true, but Reason does not explain Assertion
   c. Assertion is true, Reason is false
   d. Assertion is false, Reason is true

Answer: a. Assertion and Reason are true, and Reason explains Assertion

The law of demand explains the negative slope of the demand curve.

Q20. Assertion: A vertical demand curve is perfectly inelastic.

Reason: Quantity demanded does not change when price changes.

1. Assertion and Reason are true, and Reason explains Assertion
   b. Assertion and Reason are true, but Reason does not explain Assertion
   c. Assertion is true, Reason is false
   d. Assertion is false, Reason is true

Answer: a. Assertion and Reason are true, and Reason explains Assertion

Perfectly inelastic demand has elasticity equal to zero.

Section B: Very Short Answer Questions from Theory of Consumer Behaviour Important Questions

Very short answers from this chapter usually ask for definitions and direct formulas. Keep answers crisp and use examples where needed.

Q21. What is utility class 12 microeconomics?

Utility class 12 microeconomics means the want-satisfying capacity of a commodity.

It is subjective because different consumers may get different satisfaction from the same good.

Q22. Define total utility and marginal utility class 12.

Total utility is the total satisfaction obtained from consuming a given quantity of a commodity.

Marginal utility is the change in total utility when one additional unit is consumed.

Formula:

MU(n) = TU(n) - TU(n-1)

Q23. State the law of diminishing marginal utility class 12.

The law of diminishing marginal utility states that marginal utility falls as a consumer consumes more units of a commodity.

This happens when consumption of other commodities remains constant.

Q24. What is an indifference curve class 12?

An indifference curve class 12 is a curve that joins all bundles giving the consumer equal satisfaction.

The consumer is indifferent among all points on the same indifference curve.

Q25. What is a budget set?

Budget set is the collection of all bundles that a consumer can buy with given income and market prices.

It includes bundles on and below the budget line.

Q26. What is a budget line class 12?

Budget line class 12 is a straight line showing all bundles that cost exactly equal to the consumer’s income.

Formula:

p1x1 + p2x2 = M

Q27. What is consumer equilibrium class 12?

Consumer equilibrium class 12 is the point where the consumer gets maximum satisfaction from the budget set.

It occurs where the budget line is tangent to the highest possible indifference curve.

Section C: Short Answer Questions from Class 12 Micro Economics Chapter 2 Important Questions

Short answer questions usually test relationships between concepts. Use formulas, diagrams and examples where useful.

Q28. Explain the relationship between total utility and marginal utility.

Total utility and marginal utility are closely related.

Marginal utility is the addition to total utility from consuming one more unit. When MU is positive, TU increases. When MU becomes zero, TU is maximum or constant at that point. When MU becomes negative, TU starts falling.

Example:

If TU from 4 units is 24 and TU from 5 units is 24, then MU of the 5th unit is 0.

So, TU stops increasing when MU becomes zero.

Q29. Why does marginal utility diminish as consumption increases?

Marginal utility diminishes because the intensity of desire falls with each extra unit.

For example, the first glass of water gives high satisfaction to a thirsty person. The second glass gives less satisfaction. After several glasses, another glass may give no satisfaction.

This explains why a consumer is willing to pay less for additional units of the same good.

Q30. Explain three features of indifference curve class 12.

Three features of indifference curve class 12 are:

1. It slopes downward from left to right.
2. A higher indifference curve gives a higher level of satisfaction.
3. Two indifference curves never intersect.

The downward slope shows that more of one good requires less of another good.

A higher curve gives more satisfaction because it contains more of at least one good.

Two curves cannot intersect because that would create contradictory preference rankings.

Q31. Why is an indifference curve convex to the origin?

An indifference curve is convex to the origin because of diminishing marginal rate of substitution.

As a consumer gets more of good X, the marginal utility of X falls. At the same time, the quantity of good Y decreases, so the marginal utility of Y rises.

Therefore, the consumer is willing to sacrifice less and less of Y for each extra unit of X.

This falling MRS gives the indifference curve its convex shape.

Q32. Explain budget line with formula and intercepts.

A budget line shows all combinations of two goods that cost exactly equal to the consumer’s income.

Formula:

p1x1 + p2x2 = M

Here, p1 is price of good 1, p2 is price of good 2, and M is income.

Horizontal intercept = M / p1

Vertical intercept = M / p2

Slope = -p1 / p2

The budget line shifts when income or prices change.

Q33. How does a change in income affect the budget line?

A change in income causes a parallel shift of the budget line when prices remain constant.

If income increases, the budget line shifts outward. The consumer can buy more of both goods.

If income decreases, the budget line shifts inward. The consumer can buy fewer bundles than before.

The slope remains unchanged because the price ratio does not change.

Q34. How does a change in the price of one good affect the budget line?

A change in the price of one good changes the slope and one intercept of the budget line.

If the price of good X falls, the consumer can buy more of X with the same income. The budget line pivots outward on the X-axis.

If the price of good X rises, the budget line pivots inward on the X-axis.

The intercept of the other good remains unchanged when its price and income remain constant.

Q35. Explain the difference between normal goods and inferior goods.

Normal goods are goods whose demand increases when consumer income rises.

Example: better quality food, branded clothes or private transport.

Inferior goods are goods whose demand falls when consumer income rises.

Example: coarse cereals may become inferior goods when income rises and consumers shift to better quality food.

The same good can be normal at low income and inferior at higher income.

Q36. Distinguish between substitutes and complements.

Substitutes move in the same direction as the related good’s price.

Complements move in the opposite direction.

Q37. Explain movement along and shift in demand curve.

Movement along a demand curve happens when the price of the same commodity changes.

If price falls, demand expands. If price rises, demand contracts.

Shift in demand curve happens when factors other than own price change.

These factors include consumer income, tastes, preferences and prices of related goods.

For example, higher income shifts demand for a normal good rightward.

Q38. What is price elasticity of demand class 12?

Price elasticity of demand class 12 measures the responsiveness of quantity demanded to a change in price.

Formula:

Price elasticity of demand = Percentage change in quantity demanded / Percentage change in price

In simple terms:

ed = (Change in quantity / Original quantity) × (Original price / Change in price)

Demand is elastic when ed is greater than 1.

Demand is inelastic when ed is less than 1.

Demand is unit elastic when ed is equal to 1.

Section D: Case-Based Questions from Class 12 Micro Economics Chapter 2

Case-based questions usually test consumer choice through examples. Identify the concept first, then connect it with the given situation.

Q39. Case Study: Budget Choice Between Bananas and Mangoes

A consumer has Rs 100. Bananas cost Rs 10 each and mangoes cost Rs 20 each. The consumer spends the entire income on these two goods.

Q39(a). Write the budget line equation.

Budget line:

10x1 + 20x2 = 100

Here, x1 means bananas and x2 means mangoes.

Q39(b). Find the maximum number of bananas the consumer can buy.

If the consumer buys only bananas:

100 / 10 = 10

The consumer can buy 10 bananas.

Q39(c). Find the maximum number of mangoes the consumer can buy.

If the consumer buys only mangoes:

100 / 20 = 5

The consumer can buy 5 mangoes.

Q39(d). Find the slope of the budget line.

Slope = -p1 / p2

Slope = -10 / 20 = -1/2

The consumer gives up half a mango for one extra banana.

Q40. Case Study: Falling Price and Demand

A student buys 5 notebooks when the price is Rs 40 each. When the price falls to Rs 30, the student buys 7 notebooks.

Q40(a). Which law is shown here?

The law of demand is shown here.

Demand rises when price falls, other things being equal.

Q40(b). What is the old expenditure?

Old expenditure = Price × Quantity

Old expenditure = 40 × 5 = Rs 200.

Q40(c). What is the new expenditure?

New expenditure = 30 × 7 = Rs 210.

Q40(d). Did total expenditure rise or fall?

Total expenditure rose from Rs 200 to Rs 210.

The fall in price increased quantity demanded enough to raise total expenditure.

Q41. Case Study: Substitute Goods

The price of coffee rises sharply. Many consumers start buying more tea because tea and coffee satisfy similar wants.

Q41(a). What type of goods are tea and coffee?

Tea and coffee are substitute goods.

One can be used in place of the other.

Q41(b). What happens to demand for tea when coffee becomes costlier?

Demand for tea rises.

Consumers shift from coffee to tea.

Q41(c). How will the demand curve of tea change?

The demand curve of tea shifts rightward.

This happens because the price of a substitute has increased.

Q41(d). Is this a movement along the demand curve of tea?

No, this is not movement along the demand curve of tea.

It is a shift because the price of a related good has changed.

Q42. Case Study: Elasticity and Expenditure

A consumer buys 20 units of a good at Rs 10 per unit. When the price rises to Rs 12, demand falls to 18 units.

Q42(a). Find percentage change in quantity demanded.

Change in quantity = 18 - 20 = -2

Percentage change in quantity = -2 / 20 × 100

Percentage change in quantity = -10%

Q42(b). Find percentage change in price.

Change in price = 12 - 10 = 2

Percentage change in price = 2 / 10 × 100

Percentage change in price = 20%

Q42(c). Find price elasticity of demand.

Price elasticity of demand = 10 / 20

Price elasticity of demand = 0.5

We use the absolute value.

Q42(d). Is demand elastic or inelastic?

Demand is inelastic.

Elasticity is less than 1.

Section E: Long Answer Questions from Theory of Consumer Behaviour Class 12

Long answers from this chapter usually ask for full explanations with diagrams or formulas. Keep the answer structured and concept-first.

Q43. Explain cardinal utility analysis and the law of diminishing marginal utility.

Cardinal utility analysis assumes that utility can be measured in numbers.

Under this approach, total utility measures total satisfaction from all units consumed. Marginal utility measures the additional satisfaction from one more unit.

Formula:

MU(n) = TU(n) - TU(n-1)

The law of diminishing marginal utility states that marginal utility falls as consumption of a commodity increases, other things remaining constant.

For example, the first mango may give high satisfaction. The second gives less satisfaction, and the third gives still less.

This law explains why demand curves slope downward. A consumer will buy more units only when the price falls because each extra unit gives lower marginal utility.

Q44. Explain ordinal utility analysis through indifference curve.

Ordinal utility analysis assumes that utility cannot be measured in numbers.

A consumer can rank bundles according to preference. If two bundles give equal satisfaction, the consumer is indifferent between them.

An indifference curve joins all bundles that give the same satisfaction. It slopes downward because more of one good must be balanced by less of another good.

It is convex to the origin because marginal rate of substitution diminishes.

A family of indifference curves is called an indifference map. A higher indifference curve represents a higher level of satisfaction.

This approach explains consumer behaviour without measuring utility in numbers.

Q45. Explain consumer equilibrium using indifference curve and budget line.

Consumer equilibrium occurs when a rational consumer chooses the best affordable bundle.

The budget line shows all bundles that the consumer can buy by spending full income. Indifference curves show the consumer’s preference ranking.

The optimum bundle lies on the highest possible indifference curve that touches the budget line.

At this point:

MRS = Price ratio

In simple form:

MRS = p1 / p2

This means the consumer’s willingness to substitute one good for another equals the market rate of substitution.

A point below the budget line is not optimum because the consumer can buy more. A point above the budget line is not affordable.

Therefore, equilibrium occurs at tangency between the budget line and an indifference curve.

Q46. Explain the law of demand using substitution effect and income effect.

The law of demand states that price and quantity demanded are negatively related, other things remaining constant.

When the price of a good falls, two effects work.

First is the substitution effect. The good becomes cheaper compared to other goods. The consumer substitutes the cheaper good for relatively expensive goods.

Second is the income effect. A fall in price increases the consumer’s real purchasing power. The consumer can now buy more with the same income.

For normal goods, both effects increase demand when price falls.

This explains why the demand curve generally slopes downward.

Q47. Explain price elasticity of demand and its relationship with total expenditure.

Price elasticity of demand measures how responsive demand is to price change.

Formula:

ed = Percentage change in quantity demanded / Percentage change in price

If ed is greater than 1, demand is elastic. Quantity changes more than price.

If ed is less than 1, demand is inelastic. Quantity changes less than price.

If ed is equal to 1, demand is unit elastic. Quantity and price change by the same percentage.

Relationship with total expenditure:

1. When demand is elastic, price and total expenditure move in opposite directions.
2. When demand is inelastic, price and total expenditure move in the same direction.
3. When demand is unit elastic, total expenditure remains unchanged.

This relationship helps predict how price changes affect seller revenue and consumer spending.

Formula-Based Revision for Important Questions Class 12 Micro Economics Chapter 2

Important Questions Class 12 Micro Economics Chapter 2 should be revised through formulas, curve logic and examples.

Total Utility and Marginal Utility Class 12

Total utility is total satisfaction from a given quantity.

Marginal utility is the change in total utility from one extra unit.

Formula:

MU(n) = TU(n) - TU(n-1)

Also:

TU(n) = MU1 + MU2 + MU3 + ... + MU(n)

Law of Diminishing Marginal Utility Class 12

As consumption increases, marginal utility from each additional unit falls.

When MU is positive, TU rises.

When MU is zero, TU is maximum or constant.

When MU is negative, TU falls.

Indifference Curve Class 12

An indifference curve joins all bundles giving equal satisfaction.

Main features:

1. It slopes downward.
2. It is convex to the origin.
3. Higher indifference curve gives higher satisfaction.
4. Two indifference curves never intersect.

Marginal Rate of Substitution Class 12

MRS is the amount of one good a consumer is willing to give up for one more unit of another good.

Formula:

MRS = Absolute change in good Y / Change in good X

MRS diminishes as the consumer gets more of good X.

Budget Line Class 12

Budget line formula:

p1x1 + p2x2 = M

Horizontal intercept:

M / p1

Vertical intercept:

M / p2

Slope:

-p1 / p2

Consumer Equilibrium Class 12

Consumer equilibrium occurs where:

Budget line touches the highest possible indifference curve.

Condition:

MRS = p1 / p2

The chosen bundle must be affordable.

Demand Curve Class 12

Demand curve shows quantity demanded at different prices.

Law of demand:

Price rises, demand falls.

Price falls, demand rises.

Other things must remain constant.

Price Elasticity of Demand Class 12

Formula:

ed = Percentage change in quantity demanded / Percentage change in price

Using original values:

ed = (Change in quantity / Original quantity) × (Original price / Change in price)

Use absolute value in interpretation.

Linear Demand Curve Class 12

Linear demand equation:

d(p) = a - bp

Here, a is demand when price is zero.

b shows the fall in demand when price rises by one unit.

Elasticity differs at different points on a straight-line demand curve.

Market Demand Class 12

Market demand is the total demand of all consumers at a given price.

Formula:

Market demand = Demand of consumer 1 + Demand of consumer 2 + ... + Demand of all consumers

Market demand curve is obtained by horizontal summation of individual demand curves.

Chapter-Wise Revision for Important Questions Class 12 Micro Economics Chapter 2

Important questions class 12 micro economics chapter 2 should be revised in six parts: utility, indifference curve, budget line, consumer optimum, demand and elasticity.

Start with utility class 12 microeconomics. Learn total utility, marginal utility and the law of diminishing marginal utility.

Next, revise indifference curve class 12. Focus on MRS, convex shape, higher satisfaction and why curves never intersect.

Then revise budget line class 12. Practise the budget equation, intercepts, slope and shifts due to income or price change.

After that, revise consumer equilibrium class 12. Remember that equilibrium occurs where the budget line is tangent to an indifference curve.

Next, revise demand curve class 12 and law of demand class 12. Understand movement along demand curve and shift in demand curve.

Finally, revise elasticity of demand class 12. Practise numerical questions and the link between elasticity and total expenditure.

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