ANAND CLASSES Study Material and Notes to learn how the resistance of a conductor depends on its length, thickness, material, and temperature. A complete guide for Class 10 Science students with easy Q&A format. It includes Q&A, FAQs, conceptual questions, MCQs with explanations, Do You Know?, a worksheet, test paper with marks distribution, and quick revision points.

🧾 Factors Affecting Resistance of a Conductor – Class 10 Science Explained (Question-Answer Format)

❓ What are the factors affecting the resistance of a conductor?

The electrical resistance of a conductor depends on the following four factors:

Length of the conductor
Area of cross-section (or thickness) of the conductor
Nature of the material of the conductor
Temperature of the conductor

Mathematically: $$R \propto \frac{l}{A}$$

❓ How does the length of a conductor affect its resistance?

The resistance of a conductor is directly proportional to its length.
This means:

If the length increases, resistance increases.
If the length decreases, resistance decreases.

Mathematically: $$R \propto l$$

So, doubling the length of a wire doubles its resistance, and halving the length halves the resistance.

👉 A long wire has more resistance, while a short wire has less resistance.

❓ How does the area of cross-section affect the resistance of a conductor?

The resistance of a conductor is inversely proportional to its area of cross-section.
This means:

If the area of cross-section increases, resistance decreases.
If the area of cross-section decreases, resistance increases.

Mathematically: $$R \propto \frac{1}{A}$$

So, a thick wire (larger area) has less resistance, and a thin wire (smaller area) has more resistance.

👉 To get:

Low resistance: Use a short, thick wire.
High resistance: Use a long, thin wire.

❓ How is resistance related to the diameter of a wire?

Since area of cross-section is related to the square of the diameter: $$R \propto \frac{1}{d^2}$$

If diameter is doubled, resistance becomes one-fourth.
If diameter is halved, resistance becomes four times.
If diameter is tripled, resistance becomes one-ninth.

❓ How does the nature of the material affect the resistance of a conductor?

Resistance depends on the type of material the conductor is made of.

Different materials have different levels of resistance even if they have the same size.
For example, a nichrome wire has about 60 times more resistance than a copper wire of the same dimensions.

👉 Materials like nichrome offer high resistance, while materials like copper offer low resistance.

❓ How does temperature affect the resistance of a conductor?

For pure metals, resistance increases with temperature.
For alloys like manganin, constantan, and nichrome, the resistance is almost unaffected by changes in temperature.

📌 FAQs: Frequently Asked Questions

❓ What is resistance?

Ans: Resistance is the property of a material that opposes the flow of electric current.

❓ Why does a longer wire have more resistance?

Ans: A longer wire offers more obstacles to the movement of electrons, increasing resistance.

❓ Which wire has less resistance: thick or thin?

Ans: A thick wire has less resistance due to a larger area of cross-section.

❓ Why are alloys used for making resistors?

Ans: Alloys like nichrome have high resistance and their resistance is unaffected by temperature, making them suitable for resistors.

💡 Conceptual Questions with Answers

❓ Why does increasing the diameter of a wire decrease its resistance?

Ans: Because area of cross-section increases with the square of the diameter. $$R \propto \frac{1}{d^2}$$

❓ Two wires A and B are made of the same material and length, but A is thicker. Which has more resistance?

Ans: Wire B has more resistance because it is thinner.

❓ A student increases the length of a wire to double. What happens to the resistance?

Ans: Resistance also doubles because $$R \propto l$$

✅ MCQs with Explanation

1. Which factor does NOT affect the resistance of a wire?

a) Length
b) Temperature
c) Shape
d) Material

Answer: c) Shape
Explanation: Resistance depends on length, temperature, and material, not shape.

2. If the area of cross-section is doubled, what happens to resistance?

a) Doubled
b) Halved
c) Unchanged
d) Tripled

Answer: b) Halved
Explanation: $$R \propto \frac{1}{A}$$

3. Which wire will have the highest resistance?

a) Short and thick
b) Long and thick
c) Long and thin
d) Short and thin

Answer: c) Long and thin
Explanation: Resistance increases with length and decreases with thickness.

Here is a set of Assertion-Reason Based Questions and Answers for the topic “Factors Affecting Resistance of a Conductor” – suitable for Class 10 Science and formatted for your WordPress website:

🧠 Assertion-Reason Based Questions

✅ Instructions:

For the questions given below, two statements are provided — Assertion (A) and Reason (R).
Read them carefully and select the correct option:

Both A and R are true, and R is the correct explanation of A.
Both A and R are true, but R is not the correct explanation of A.
A is true, but R is false.
A is false, but R is true.

🔶 Q1.

Assertion (A): A longer wire has more resistance than a shorter wire of the same material and thickness.
Reason (R): Resistance is directly proportional to the length of the wire.

Answer: ✅ Option 1
Explanation: Both statements are true and the reason correctly explains the assertion.

🔶 Q2.

Assertion (A): Resistance of a thick wire is more than that of a thin wire.
Reason (R): Resistance is inversely proportional to the area of cross-section of the wire.

Answer: ❌ Option 3
Explanation: The assertion is false because thick wires have less resistance, but the reason is true.

🔶 Q3.

Assertion (A): Nichrome is preferred over copper for making heating elements.
Reason (R): Nichrome has low resistance and does not heat up easily.

Answer: ❌ Option 3
Explanation: The assertion is true, but the reason is false. Nichrome is used because it has high resistance and heats up efficiently.

🔶 Q4.

Assertion (A): Resistance of a conductor increases with increase in temperature.
Reason (R): As temperature increases, atoms in the conductor vibrate more and obstruct electron flow.

Answer: ✅ Option 1
Explanation: Both A and R are correct, and the reason explains the assertion.

🔶 Q5.

Assertion (A): Resistance of a wire becomes four times if its diameter is doubled.
Reason (R): Resistance is inversely proportional to the square of the diameter.

Answer: ❌ Option 4
Explanation: The assertion is false. If the diameter is doubled, resistance becomes one-fourth, not four times. The reason is true.

💡 Do You Know?

Nichrome is used in electric heaters because of its high resistance and temperature stability.
Copper has very low resistance, which is why it’s used in household wiring.
Resistance is measured in ohms (Ω), named after Georg Simon Ohm.

✍️ Worksheet

Instructions: Answer the following in 1–2 sentences.

Define resistance.
What happens to resistance if the length of a wire is tripled?
Which has more resistance: copper or nichrome?
State the relation between resistance and area of cross-section.
Why does resistance increase with temperature in metals?

📝 Test Paper – 10 Marks

Q1. Define resistance.
Q2. What is the relation between resistance and length of a wire?
Q3. Give two factors that affect the resistance of a conductor.
Q4. Explain how area of cross-section influences resistance.
Q5. MCQ – Choose the correct answer (as above).

🧠 Important Points for Quick Revision

Resistance $R \propto l$ (length)
Resistance $R \propto \frac{1}{A}$ (area)
Resistance increases with temperature for metals.
Resistance is constant for alloys with temperature.
Thick, short wires = less resistance
Thin, long wires = more resistance
Unit of resistance = Ohm (Ω)