## Temperature Coefficient of Resistance MCQ (Interview-Exam) Question-Answer

**Q.1** The resistance of pure metals ___________.

**A.** Decreases with an increase in temperature

**B.** Becomes zero with an increase in temperature

**C.** Increases with an increase in temperature

**D.** Remains the same with an increase in temperature

**Ans : **Increases with an increase in temperature

**Q.2** The resistance of insulators __________.

**A.** Decreases with an increase in temperature

**B.** Becomes zero with an increase in temperature

**C.** Increases with an increase in temperature

**D.** Remains the same with an increase in temperature

**Ans : **Decreases with an increase in temperature

**Q.3** Which of the following statements are true about insulators?

**A.** Insulators have a negative temperature coefficient

**B.** Insulators have zero temperature coefficient

**C.** Insulators have a positive temperature coefficient

**D.** Insulators have infinite temperature coefficient

**Ans : **Insulators have a negative temperature coefficient

**Q.4** Which of the following statements are true about metals?

**A.** Metals have a negative temperature coefficient

**B.** Metals have infinite temperature coefficient

**C.** Metals have a positive temperature coefficient

**D.** Metals have zero temperature coefficient

**Ans : **Metals have a positive temperature coefficient

**Q.5** A copper coil has a resistance of 200 ohms when its mean temperature is 0 degree centigrade. Calculate the resistance of the coil when its mean temperature is 80 degree centigrade. Temperature coefficient of copper is 0.004041 centigrade^-1

**A.** 264.65 kilo-ohm

**B.** 286.65 kilo-ohm

**C.** 264.65 ohm

**D.** 286.65 ohm

**Ans : **264.65 ohm

**Explanation: ** R=R0(1+α dT) = 200(1+ 0.004041*80) = 264.65 ohm.

**Q.6** What is the unit of temperature coefficient?

**A.** ohm-centigrade

**B.** centigrade

**C.** ohm/centigrade

**D.** centigrade^-1

**Ans : **centigrade^-1

**Q.7** The rise or fall in resistance with the rise in temperature depends on ________.

**A.** The current in the metal

**B.** Does not depend on any factor

**C.** The property of the conductor material

**D.** Property of material as well current in that material

**Ans : **The property of the conductor material

**Q.8** The temperature of a coil cannot be measured by which of the following methods?

**A.** Increase in resistance of the coil

**B.** Calorimeter

**C.** Thermometer

**D.** Thermo-junctions embedded in the coil

**Ans : **Calorimeter

**Q.9** Materials having resistance almost equal to zero is _______.

**A.** Conductor

**B.** Insulators

**C.** Semi-conductor

**D.** Superconductors

**Ans : **Superconductors

**Q.10** If the temperature is increased in semi-conductors such that the resistance incessantly falls, it is termed as _______.

**A.** Zener breakdown

**B.** Avalanche runway

**C.** Avalanche breakdown

**D.** Thermal runway

**Ans : **Thermal runway

## Temperature Coefficient of Resistance

**1. Definition:** The temperature coefficient of resistance is a measure of how much the electrical resistance of a material changes with temperature. It is denoted by the symbol α (alpha) and is expressed in units of ohms per degree Celsius (Ω/°C).

**2. Positive and Negative Coefficients:** Materials can exhibit either positive or negative temperature coefficients. A positive TCR means that the resistance increases with temperature, while a negative TCR indicates a decrease in resistance as the temperature rises.

**3. Metals and Alloys:** Most metals and common conductors like copper and aluminum have positive temperature coefficients. As temperature increases, the metal atoms vibrate more, leading to increased electron scattering and higher resistance.

**4. Semiconductors:** Semiconductors typically have a negative temperature coefficient. As temperature rises, more charge carriers (electrons or holes) are released, resulting in increased conductivity and reduced resistance.

**5. Calculation:** The TCR is often specified as the percentage change in resistance per degree Celsius. The formula is given by:

\[ \alpha = \frac{1}{R_0} \cdot \frac{\Delta R}{\Delta T} \]

where:

**\(\alpha\):**the temperature coefficient of resistance.**\(R_0\):**the initial resistance at temperature \(T_0\).**\(\Delta R\):**the change in resistance.**\(\Delta T\):**the change in temperature.

**6. Temperature Compensation:** Understanding the TCR is essential in applications where precise resistance values are required across a range of temperatures. Engineers often use materials with specific temperature coefficients for temperature compensation in electronic components.

**7. Effects on Circuit Performance:** Changes in resistance due to temperature variations can impact the performance of electronic circuits. Careful consideration of the TCR is necessary to ensure stability and accuracy in various applications, such as sensors, amplifiers, and precision resistors.

**8. Selection of Components:** When designing circuits, engineers select resistors or other components with TCR values suitable for the intended operating conditions. This ensures that the circuit’s performance remains consistent over a specified temperature range.

**9. Calibration:** In certain applications, especially those requiring high precision, calibration procedures may be implemented to account for the effects of temperature on resistance. This ensures accurate measurements and reliable operation under varying temperature conditions.