What is the Effect of Temperature on Resistance?

S6-SA3-0200

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

The effect of temperature on resistance describes how the electrical resistance of a material changes when its temperature changes. Generally, for most conductors like metals, resistance increases as temperature rises because the electrons collide more often.

Simple Example

Quick Example

Imagine a busy street market in India. When it's cool in the morning, people (electrons) can move easily. But as the sun gets hotter in the afternoon, the market gets more crowded and people move slower, bumping into each other more often. This 'difficulty in moving' is like increased resistance.

Worked Example

Step-by-Step

Let's calculate the resistance of a copper wire at 50°C if its resistance at 20°C is 5 ohms, and its temperature coefficient of resistance is 0.0039 per °C.

Step 1: Identify the given values.
Initial resistance (R0) = 5 ohms at T0 = 20°C.
Final temperature (T) = 50°C.
Temperature coefficient (alpha) = 0.0039 per °C.

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Step 2: Calculate the change in temperature (ΔT).
ΔT = T - T0 = 50°C - 20°C = 30°C.

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Step 3: Use the formula for resistance change with temperature: R = R0 * (1 + alpha * ΔT).

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Step 4: Substitute the values into the formula.
R = 5 * (1 + 0.0039 * 30).

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Step 5: Calculate the term inside the parenthesis.
0.0039 * 30 = 0.117.
1 + 0.117 = 1.117.

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Step 6: Multiply by the initial resistance.
R = 5 * 1.117 = 5.585 ohms.

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Answer: The resistance of the copper wire at 50°C is 5.585 ohms.

Why It Matters

Understanding how temperature affects resistance is crucial for designing reliable electronic circuits and devices. Engineers use this knowledge to create sensors for measuring temperature, build efficient power systems, and ensure that our mobile phones and computers don't overheat, impacting performance. It's vital for careers in electronics, space technology, and even medicine.

Common Mistakes

MISTAKE: Assuming all materials behave the same way with temperature. | CORRECTION: Remember that conductors (like metals) usually increase resistance with temperature, while semiconductors (like silicon) and insulators often decrease resistance.

MISTAKE: Forgetting to use the correct temperature difference (ΔT) in calculations. | CORRECTION: Always calculate the difference between the final and initial temperatures, not just use the final temperature directly in the formula.

MISTAKE: Confusing resistance with resistivity. | CORRECTION: Resistance (R) depends on the material's dimensions (length, area) and its resistivity (rho). Resistivity is an intrinsic property of the material, which changes with temperature, and thus affects resistance.

Practice Questions

Try It Yourself

QUESTION: A nichrome wire has a resistance of 10 ohms at 0°C. If its temperature coefficient of resistance is 0.0004 per °C, what will its resistance be at 100°C? | ANSWER: 10.4 ohms

QUESTION: The resistance of a thermistor (a type of semiconductor) decreases from 2000 ohms to 500 ohms when its temperature increases from 20°C to 50°C. Does this material behave like a conductor or a semiconductor in terms of temperature and resistance? | ANSWER: It behaves like a semiconductor, as its resistance decreased with an increase in temperature.

QUESTION: A copper wire has a resistance of 8 ohms at 25°C. Its temperature coefficient is 0.0039 per °C. If a circuit requires the wire's resistance to be no more than 8.5 ohms, what is the maximum temperature the wire can reach? | ANSWER: Approximately 41.02°C

MCQ

Quick Quiz

For most pure metallic conductors, what happens to their electrical resistance as the temperature increases?

It decreases

It increases

It remains constant

It first decreases, then increases

The Correct Answer Is:

For most metallic conductors, atoms vibrate more vigorously at higher temperatures, causing more frequent collisions with moving electrons, thus increasing resistance. Options A, C, and D are incorrect for pure metals.

Real World Connection

In the Real World

This concept is vital in designing temperature sensors called RTDs (Resistance Temperature Detectors), often used in industrial ovens, refrigerators, and even in some medical devices in India to precisely monitor temperature. Also, in your mobile phone, engineers consider how the internal temperature rise due to heavy usage might affect the resistance of components, potentially slowing down the phone or reducing battery life.

Key Vocabulary

Key Terms

RESISTANCE: The opposition to the flow of electric current | TEMPERATURE COEFFICIENT OF RESISTANCE: A measure of how much a material's resistance changes per degree Celsius change in temperature | CONDUCTOR: A material that allows electric current to flow easily | SEMICONDUCTOR: A material with electrical conductivity between that of a conductor and an insulator

What's Next

What to Learn Next

Now that you understand how temperature affects resistance, you're ready to explore 'Ohm's Law' and 'Series and Parallel Circuits'. These concepts will help you apply what you've learned to calculate current and voltage in real-world electrical systems, building on your foundational knowledge of resistance.