This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Operation of Strain Gauges”.
1. Electrical strain gauge works on the principle of __________
a) variation of resistance
b) variation of capacitance
c) variation of inductance
d) variation of area
Explanation: An electrical strain gauge works on the basis of change in resistance as a function of strain. The wire resistance increases with tension and reduces with compression.
2. The strain gauge is not bonded to the specimen.
Explanation: The gauge is under the same strain as that the specimen under test. As a result the strain gauge is bonded to the specimen.
3. Bonding element in a strain gauge must have __________
a) zero insulation resistance
b) low insulation resistance
c) high insulation resistance
d) infinite insulation resistance
Explanation: In a strain gauge, the bonding element must have a high value of insulation resistance. It should be immune to effects of moisture and must also have the ability to transmit strain.
4. Dynamic strain measurements use __________
a) brass iron alloy
b) iron aluminium alloy
c) nickel cadmium alloy
d) nickel chromium alloy
Explanation: Nickel chromium alloy is also known as a nichrome alloy. It contains 80 % of Nickel and 20 % of Chromium. Platinum is used for the temperature compensation of nickel chromium alloys.
5. Commonly used elements for wire strain gauges are __________
a) nickel and copper
b) nickel and gold
c) gold and brass
d) silver and aluminium
Explanation: Nickel and copper are the most commonly used elements for wire strain gauges. They comprise of 45 % of Nickel and 55 % of Copper. They exhibit a high value of specific resistance.
6. Cement is classified under __________
a) 4 types
b) 2 types
c) 6 types
d) 8 types
Explanation: Cement can be divided into two broad categories. They are as follows:
Solvent setting cement
Chemically reacting cement.
7. Proper functioning of a strain gauge depends on __________
d) length of wire
Explanation: A strain gauge works properly only if the bonding material used is durable and keeps the gauge together to the surface of the material that is being tested.
Explanation: Gauge factor in a strain gauge is given by the relation
where, S is the gauge factor
R is the gauge wire resistance
∆R is the change in resistance
l is the length of the wire in unstressed condition
∆l is the change in length of the wire.
Explanation: Poisson’s ratio is given by the relation
where, d is the diameter of the cross-section of the wire
∆d is the change in the diameter of cross-section of the wire.
10. Proper bonding causes errors in strain gauges.
Explanation: Strain gauge is fixed onto the specimen by means of a bonding element. Cement is the commonly used adhesive. It transfers the strain from the specimen to the gauge sensing element.
Sanfoundry Global Education & Learning Series – Electrical Measurements.
To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.