Theory of Demand – Chapter 2 | Law of Demand | Class 11 (New Syllabus 2019) | Part 1 Created by Dr. Irfana Samdani This lecture explains the fundamental concepts of Theory of Demand in a simple, clear, and easy-to-understand manner. Designed for approximately 20 minutes, it provides a comprehensive introduction to the Law of Demand and related concepts in Microeconomics and Business Economics. Topics Covered Meaning of Utility Meaning and Definition of Demand Characteristics of Demand Determinants of Demand Substitute and Complementary Goods Normal, Inferior, and Giffen Goods Law of Demand Assumptions of the Law of Demand Demand Schedule and Demand Curve Suitable For Class 11 Commerce (New Syllabus 2019) Class 12 Commerce Business Economics Microeconomics CA Foundation (formerly CPT) B.Com and other Commerce & Management courses The lecture uses practical examples and simple explanations to help students understand the relationship between price and quantity demanded, making it easier to grasp the core principles of demand analysis. If you find this lecture helpful, please Like, Share, and Subscribe to the World of Economics channel for more lectures on Economics and Commerce. **Lecture by Dr. Irfana Samdani** Hello students, welcome to my lecture. Today, we will discuss **Chapter 2: Theory of Demand**. ## Lecture Outline In this lecture, we will cover: * Meaning of Demand * Determinants of Demand * Law of Demand --- # Understanding Utility Before we discuss the meaning of demand, it is important to understand the concept of **utility**. **Utility** is the **want-satisfying power of a commodity**. Whenever a consumer uses or consumes a commodity, they derive satisfaction from it. This satisfaction is known as **utility**. Therefore, utility can be defined as: > **Utility is the satisfaction derived from the consumption of a commodity.** ## Nature of Utility Utility is **subjective**, meaning it differs from one person to another. ### Example 1 Consider two individuals: * One person likes chocolate. * The other person does not. If both are offered chocolate, the person who likes chocolate will derive greater satisfaction (higher utility), whereas the person who dislikes chocolate will derive less satisfaction (lower utility). ### Example 2 Now consider the same person consuming a chocolate, such as **Cadbury Dairy Milk Silk**. * The first bite provides a very high level of satisfaction. * As the person continues eating, the satisfaction from each additional bite gradually decreases. * By the sixth or last bite, the satisfaction is much lower than that derived from the first bite. This illustrates that the utility obtained from consuming additional units of the same commodity gradually declines. Generally, the higher the utility obtained from a commodity, the stronger the consumer's desire to possess it. --- # Meaning of Demand It is important to understand that **desire and demand are not the same**. A person may desire many goods, but desire alone does not constitute demand. A desire becomes demand only when certain conditions are fulfilled. These conditions are: 1. **Purchasing Power** – The consumer must have sufficient income or resources to purchase the commodity. 2. **Willingness to Spend** – The consumer must be willing to spend money to obtain the commodity. 3. **Availability of the Commodity** – The commodity must be available in the market. ## Definition of Demand Demand may be defined as: > **The quantity of a commodity that a consumer is willing and able to purchase at a given price during a specified period of time.** ### Characteristics of Demand The important features of demand are: * Quantity of the commodity desired * Willingness to buy * Ability to purchase * Purchase at a given market price * Purchase during a specific period (such as a week or a month) --- # Determinants of Demand The **demand function** expresses the relationship between demand and the various factors that influence it. Demand for a commodity depends upon: * Price of the commodity * Prices of related goods * Consumer's income * Consumer's tastes and preferences --- ## 1. Price of the Commodity Price is the most important determinant of demand. Normally, demand varies inversely with price. --- ## 2. Prices of Related Goods Related goods are of two types: ### (a) Substitute Goods Substitute goods are goods that can be used in place of one another. **Examples:** * Coca-Cola and Pepsi * Tea and Coffee Suppose a consumer is equally satisfied with Coca-Cola and Pepsi. If the price of Coca-Cola increases while the price of Pepsi remains unchanged, consumers are likely to purchase more Pepsi. Thus, the demand for Pepsi increases. --- ### (b) Complementary Goods Complementary goods are goods that are used together. **Examples:** * Ball pen and refill * Car and petrol The utility of one good depends on the availability of the other. For example, a ball pen without a refill is useless, and a refill without a pen body is also of little use. Therefore, if the price of refills increases, the demand for ball pens decreases. --- ## 3. Taste and Preferences Consumer preferences also affect demand. * If consumers develop a positive preference for tea, the demand for tea increases. * If consumers develop a dislike for coffee, the demand for coffee decreases. --- ## 4. Income of the Consumer Consumer income significantly influences demand. ### (a) Normal Goods For normal goods, an increase in income leads to an increase in demand. **Example:** Milk As consumers earn more income, they generally purchase more milk or better-quality milk. --- ### (b) Inferior Goods For inferior goods, an increase in income leads to a decrease in demand. **Example:** Jowar and Wheat A consumer who previously purchased jowar due to limited income may switch to wheat after their income increases. As a result, the demand for jowar declines. Inferiority refers to affordability, not product quality. --- ### (c) Giffen Goods Giffen goods are a special category of inferior goods in which demand increases even when the price increases due to exceptional consumer behavior. --- # Law of Demand The **Law of Demand** states: > **Other things remaining constant, when the price of a commodity increases, its quantity demanded decreases. Conversely, when the price decreases, its quantity demanded increases.** Thus, **price and quantity demanded are inversely related.** --- ## Assumptions of the Law of Demand The phrase **"other things remaining constant"** means that the following factors do not change: * Consumer income * Prices of related goods * Consumer tastes and preferences * Other factors affecting demand Only the price of the commodity changes. --- # Why Does the Law of Demand Operate? When the price of a commodity increases, some consumers can no longer afford it. Consequently, the quantity demanded decreases. Similarly, when the price decreases, more consumers can afford the commodity, leading to an increase in quantity demanded. --- ## Illustration Suppose you plan to buy a smartphone costing **₹80,000**. When you visit the showroom, you learn that due to higher taxes, the price has increased to **₹1,00,000**. If your income remains unchanged, you may postpone your purchase. Now suppose your employer informs you that your salary has increased and you will receive **₹50,000 in arrears**. Because your income has increased, you may now decide to purchase the smartphone despite its higher price. This example demonstrates that when income changes along with price, the Law of Demand may not hold. Therefore, the law operates only when **other factors remain constant**. --- # Demand Schedule | Price (₹) | Quantity Demanded | | --------- | ----------------- | | 5 | 100 | | 10 | 80 | | 15 | 60 | The table shows that as the price increases, the quantity demanded decreases. --- # Demand Curve The demand curve is drawn with: * **Price** on the **Y-axis** * **Quantity Demanded** on the **X-axis** Using the above data: * At ₹5, quantity demanded is 100. * At ₹10, quantity demanded is 80. * At ₹15, quantity demanded is 60. Joining these points forms a **downward-sloping demand curve**, indicating the inverse relationship between price and quantity demanded. Whenever one variable increases while the other decreases, the graph slopes downward from left to right. --- # Conclusion To summarize: * Utility is the satisfaction derived from consuming a commodity. * Demand is not merely desire; it requires willingness, ability to purchase, and availability of the commodity. * Demand is influenced by price, income, prices of related goods, and consumer preferences. * According to the Law of Demand, price and quantity demanded have an inverse relationship, provided all other factors remain constant. In the next lecture, we will discuss: * Factors affecting demand * Change in quantity demanded * Extension and contraction of demand * Increase and decrease in demand Thank you for watching this lecture. I hope you found it informative. If you have any questions or doubts, please feel free to ask. If you enjoyed this lecture, please like, share, and subscribe to the **World of Economics** channel for more educational content.