Question

With a \(1^\circ\text{C}\) change in temperature, the emf changes by

• A. \( \text{0.1 mV} \)
• B. \( \text{0.2 mV} \)
• C. \( \text{0.5 mV} \)
• D. \( \text{0.8 mV} \)

Hint:

Sensor sensitivity to temperature changes is often in the microvolt to millivolt range per degree Celsius. Knowing typical values for common sensors like thermocouples helps in quick estimation during exams.

Answer 1

The Correct Option is B

To solve this problem, let's explore how temperature changes affect the electromotive force (emf) in certain materials, typically used in thermoelectric applications.

1. What is Electromotive Force (emf)?

Electromotive force (emf) refers to the potential difference that causes current to flow in a circuit. In thermoelectric devices, emf is often generated in response to changes in temperature, as the electrical properties of materials change with temperature.

2. Explanation of Each Option:

- Option 1: "0.1 mV" – This is incorrect. A 1°C change in temperature typically does not result in such a small change in emf in most standard thermoelectric materials. The change would be higher.

- Option 2: "0.2 mV" – This is the correct answer. A 1°C change in temperature in many thermoelectric materials, such as certain types of thermocouples, leads to a typical emf change of approximately 0.2 mV. This value is commonly observed in materials like copper-constantan pairs in thermocouples.

- Option 3: "0.5 mV" – This is incorrect. While a change of 0.5 mV is observed in some materials, it is typically associated with a different temperature range or type of thermocouple, not a standard 1°C change.

- Option 4: "0.8 mV" – This is incorrect. A 0.8 mV change is larger than what is typically observed for a 1°C change in temperature for most common thermoelectric materials.

3. Why This Matters:

Understanding how temperature affects emf is essential for designing thermoelectric sensors and devices that rely on temperature gradients to generate electrical energy or measure temperature accurately, such as thermocouples and temperature sensors in industrial and scientific applications.

4. Final Answer:

The correct emf change with a 1°C temperature change is 0.2 mV.