Strain Gauge Measurement MCQ

Strain Gauge Measurement MCQ

Strain Gauge Measurement MCQ, MCQ on Strain Gauge, Objective Questions on Strain Gauge Measurement, Gate MCQ on Strain Gauge Measurement, Strain Gauge Measurement-based Gate Objectives Questions with Answer, Engineering MCQ, Electronics Instrumentation MCQ

Objective Type Questions

1. In wire wound strain gauges, the change in resistance on application of strain is mainly due to

• change in length of wire
• change in diameter of the wire
• change in both length and diameter of the wire
• change in resistivity

Answer: change in both length and diameter of the wire

2. Unbonded strain gauges are

• exclusively used for transducer applications
• exclusively used for stress analysis
• commonly used for both transducer applications as well as for stress analysis
• none of the above

Answer: exclusively used for transducer applications

3. The gauge factor is defined as

• $\frac{\Delta L/L}{\Delta R/R}$
• $\frac{\Delta R/R}{\Delta L/L}$
• $\frac{\Delta R/R}{\Delta D/D}$
• $\frac{\Delta R/R}{\Delta \rho /\rho }$

where L, D, ρ and R are respectively the length, diameter, resistivity and resistance of strain gauge.

Answer: $\frac{\Delta R/R}{\Delta L/L}$

4. For wire wound strain gauges the approximate value of gauge factor is

• $1+2\Delta \rho /\rho$
• $1+2\Delta R/R$
• $1+2\nu$
• $1+2\Delta D/D$

where ρ, R, v and D are respectively resistivity, resistance, poisson’s ratio and diameter.

Answer: $1+2\nu$

5. Metal foil type of strain gauges are superior to wire wound metal strain gauges because

• they have a higher heat dissipation capacity
• they have a larger surface area which makes the bonding easier
• they can be fabricated economically using techniques which are similar to micro-electronic circuitry
• all of the above

6. Metal foil gauges use fat end turns in order to

• reduce transverse sensitivity
• reduce longitudinal sensitivity
• reduce cross-sensitivity
• all of the above

7. In semi-conductor strain gauges, the change in resistance on application of strain

• is much higher than that in the case of metal strain gauges and this is mainly due to change in dimensions
• is much higher than that in the case of metal strain gauges and this is mainly due to change in resistivity
• is lower than that in the case of metal strain gauges
• none of the above

Answer: is much higher than that in the case of metal strain gauges and this is mainly due to change in resistivity

8. In semi-conductor strain gauges, when a tensile strain is applied

• resistance increases in N-type of materials
• resistance increases in P-type materials
• resistance increases in both P and N-type materials
• resistance decreases in both P and N-type materials

Answer: resistance increases in P-type materials

9. Dummy strain gauges are used for

• compensation of temperature changes
• increasing the sensitivity of bridge in which they are included
• compensating for differential expansion
• calibration of strain gauges

10. The output of a strain gauge bridge using two active strain rages used in Poisson’s configuration is

• $\frac{\nu G_{f}\epsilon e_{i}}{4}$
• $\frac{\nu G_{f}\epsilon e_{i}}{2}$
• $\frac{(1+\nu) G_{f}\epsilon e_{i}}{2}$
• $\frac{(1+\nu) G_{f}\epsilon e_{i}}{4}$

where υ = Poisson’s ratio, Gf = gauge factor, ε = strain and ei = excitation voltage of bridge.

Answer: $\frac{(1+\nu) G_{f}\epsilon e_{i}}{4}$

11. Hoop stresses act

• in axial direction
• in both radial and axial directions
• none of the above

12. Strain gauge rosettes are used

• when the direction of principal stress is known
• when the direction of principal stress is not known
• when the direction of hoop stress is not known
• when the direction of longitudinal stress is not known

Answer: when the direction of principal stress is not known

13. Error due to cross-sensitivity is on account of

• A part of the grid is unintentionally aligned in the longitudinal direction and senses the strain in that direction. This strain gets superimposed on the transverse strain.
• A part of the grid is unintentionally aligned along the transverse direction and senses the strain in that direction. This strain gets superimposed on the longitudinal strain.
• Specimen attaining elastic limit following which strains as great as 10 to 15 percent occur.
• All of the above.

Answer: A part of the grid is unintentionally aligned along the transverse direction and senses the strain in that direction. This strain gets superimposed on the longitudinal strain.

14. The limitations on use of strain gauges at high temperatures are due to

• deterioration of grid material
• use of weldable type gauges
• decomposition of cement and carrier materials
• use of flame spraying

Answer: decomposition of cement and carrier materials

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