This set of Basic Electronics Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Transducers – Thermistor and Thermocouple”.
1. Thermistor’s resistance is ________ sensitive.
a) Temperature
b) Light
c) Pressure
d) Heat
View Answer
Explanation: The thermistor is also called as thermal resistor. It is two terminal semi-conductor device whose resistance is temperature sensitive. The value such resistor decreases with increase of the temperature.
2. Thermistors are not made with _______
a) Cobalt
b) Nickel
c) Copper
d) Platinum
View Answer
Explanation: Thermistors are generally made with the materials like cobalt, nickel, copper. The other materials that are used to make the thermistors are iron, uranium and manganese. Platinum is not used to make the thermistors.
3. The temperature coefficient of resistance for the thermistor is _________
a) High
b) Low
c) Zero
d) Moderate
View Answer
Explanation: The temperature coefficient of the resistance for the thermistor is high because the thermistors are the temperature sensitive devices. Their resistance changes with small change in temperature.
4. The thermistor can be made an ideal transducer by increasing the temperature about _______ per degree centigrade.
a) 3-5%
b) 1-2%
c) 2-4%
d) 4-5%
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Explanation: The thermistors can be made an ideal transducer by increasing the temperature of the thermistor by 3-5% per degree centigrade. By increases there will be change in resistance that will decrease so that conduction increases.
5. The temperature coefficient of resistance for thermistor is always ________
a) Positive
b) Negative
c) Positive and Negative
d) Zero
View Answer
Explanation: The temperature coefficient of resistance for thermistor is always negative. The thermistor has high temperature coefficient of resistance.
6. The resistance of the thermistor at any temperature T is given by ________
a) RT=R0 exp β(T – 1/T0)
b) RT=R0 exp β(1/T – T0)
c) RT=R0 exp β(1/T – 1/T0)
d) RT=R0 exp β(1 – 1/T0)
View Answer
Explanation: The resistance of the thermistor at any temperature T is given by RT=R0 exp β(1/T – 1/T0), where RT = Thermistor resistance at temperature T in kelvin, R0 = thermistor resistance at temperature T0 in kelvin, β = a constant determine by calibration.
7. At high temperature the resistance of the thermistor is given by RT=R0 exp β.T.
a) True
b) False
View Answer
Explanation: Generally, the resistance of the thermistor is given by RT=R0 exp β(1/T – 1/T0). When the temperature is high then the initial temperature 1/T0 is negligible. So, the equation will become RT=R0 exp β(1/T).
8. The temperature of the thermistor can be changed ________
a) Internally
b) Externally
c) Neither internally nor externally
d) Internally and externally
View Answer
Explanation: The temperature of the thermistor can be change both internally and externally. When the current is increased then the temperature is increased there by reducing the resistance at terminals.
9. When the external heat source is applied to the thermistor then the temperature will _____
a) Increase
b) Decrease
c) Zero
d) Remains constant
View Answer
Explanation: When the external heat is applied to the thermistor then the temperature of the body will be increased. It results in resistance drop. This type of actions lend itself to well controlled mechanism.
10. Which of the following parameters is not useful for characterizing the thermistor?
a) Time constant
b) Dissipation constant
c) Resistance ratio
d) Temperature constant
View Answer
Explanation: There are three parameters that determine the characteristics of the thermistor. They are time constant, resistance ratio and dissipation constant. The temperature constant have no effect on the characteristics of the thermistor.
Sanfoundry Global Education & Learning Series – Basic Electronics Engineering.
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