# Electrical Measurements Questions and Answers – Resistance Temperature Detector

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Resistance Temperature Detector”.

1. Resistance temperature detector is ___________
a) a electrical transducer
b) a mechanical transducer
c) a chemical transducer
d) a physical transducer

Explanation: Resistance temperature detector is an electrical transducer. It is used for measuring the variation in temperature. It is also known as a resistance thermometer.

2. Relation between temperature and resistance of a conductor is ________
a) Rt = Rref [1+t]
b) Rt = Rref [1+α∆t]
c) Rt = Rref [1-αt]
d) Rt = Rref [1-t]

Explanation: The relationship between temperature and resistance of a conductor is given by
Rt = Rref [1+α∆t]
where, Rt is the resistance of the conductor at t°C.
Rref is the resistance of the conductor at reference temperature
α is the temperature coefficient of resistance
∆t is the difference between the temperature being measured and the reference temperature.

3. Sensing element in the thermometer must provide ________
a) small change in resistance
b) no change in resistance
c) large change in resistance
d) infinite change in resistance

Explanation: The sensing element in a thermometer must give a large change in the resistance for a given change in the temperature.

4. Platinum is used for industrial applications because ________
a) it is cheap
c) it is a noble metal
d) it gives accurate measurements

Explanation: In industrial applications, platinum is used due to its accuracy in providing measurements. It is also reproducible. Platinum element can be used for the measurement of temperatures of about 1000 K.

5. Resistance thermometer provides the change in electrical resistance.
a) True
b) False

Explanation: A resistance thermometer provides a change in the electrical resistance with respect to a variation in the temperature. Basically resistance thermometers work on the principle of change in the electrical resistance with variation in the temperature.
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6. If the sensing element is large, then less amount of heat is required.
a) True
b) False

Explanation: When the sensing element in a resistance thermometer is small in size, then less quantity of heat is required to raise the temperature. Platinum, nickel and copper are the commonly used metals for measuring temperature.

7. Most metallic conductors have a ________
a) neutral temperature coefficient of resistance
b) negative temperature coefficient of resistance
c) positive temperature coefficient of resistance
d) zero temperature coefficient of resistance

Explanation: In general metallic conductors have a positive temperature coefficient of resistance. The resistance increases with an increase in temperature.

8. In a temperature sensing element ________
a) low value of α is required
b) infinite value of α is required
c) α must be zero
d) high value of α is required

Explanation: In order to achieve a large change in the value of resistance for a small change in the value of temperature, high value of α is required. Change in resistance is measured through a Wheatstone’s bridge.

9. Nickel and its alloys can be used over a temperature range of ________
a) 100 to 450 K
b) 10 to 50 K
c) 0 to 25 K
d) 5 to 15 K

Explanation: Temperature sensors constructed using nickel and its alloys can be used in the temperature range of 100 to 450 K. Compared to platinum, they are less expensive. They have a comparatively higher temperature coefficient that increases with temperature.

10. How can corrosion be prevented in a resistance thermometer?
a) by immersing the setup in oil
b) by enclosing the elements in a glass tube
c) by using guard rings
d) by painting the elements

Explanation: Corrosion can be eliminated in a resistance thermometer by enclosing the elements in a protective tubular glass made of pyrex, quartz or crystal depending upon the temperature range.

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