# Basic Electronics Engineering Questions and Answers – Transducers – LVDT and Electrical Strain Gauges

This set of Basic Electronics Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Transducers – LVDT and Electrical Strain Gauges”.

1. The most widely used inductance transducer is ___________
a) Linear variable transformer
b) Linear variable differential transformer
c) Linear differential transformer
d) Linear integrated transformer

Explanation: The most widely used inductance transducer is linear variable differential transformer. It is well known as the LVDT. It has a primary coil and secondary coils and a rod shaped magnetic core that are positioned at the centrally inside the coil.

2. The primary coil of LVDT are fed with ______
a) Alternating current
b) Direct current
c) Inductance
d) Voltages

Explanation: The primary coil of LVDT are fed with alternating current. After applying the alternating current to the primary coils, then the voltages V01 and V02 are induced in the secondary coil of the LVDT.

3. The primary and secondary coils of LVDT are connected in series.
a) False
b) True

Explanation: Yes, the primary and secondary coils of LVDT are connected in series. The output voltage is V0 = V01 – V02. If the core placed ideally in the central position. As, the V01=V02, so V0=0. In practice due to incomplete balance, the residual voltage usually remains with core.

4. The output voltage produced by the displacement of the core is _____ over a considerable range.
a) Non-linear
b) Parabolic
c) Linear
d) Rectangular parabola

Explanation: The output voltage produced by the displacement of the core is linear over a considerable range. When the core is displaced from the null position, the induced voltage in the secondary towards which the core moved increases and secondary decreases that results in differential output from transformer.

5. If the core moves over the centre position, then the voltage phase changes by______
a) 120°
b) 150°
c) 180°
d) 270°

Explanation: If the core moves over the centre position, then the voltage phase changes by 180°. LVDT provides the continuous resolution and show low hysteresis and hence repeatability is excellent under all conditions.

6. There is no friction because there is no ________
a) Sliding contacts
b) Noise
c) Potential energy
d) Static energy

Explanation: There is no friction because there is no sliding contacts. There is also no noise due to no sliding contacts. The induced voltage in the secondary towards which the core moved increases and secondary decreases.

7. LVDT is sensitive to _______
a) Temperature
b) Pressure
c) High voltages
d) Low voltages

Explanation: LVDT is sensitive to vibrations and temperature. The receiving instrument must be selected to operate on alternating current signals or a demodulator network must be used if a dc output required.

8. The force summing device is used to change the ___________
a) Distance between the parallel plates of capacitor
b) Area of the parallel plates of capacitor
c) Dielectric material
d) Relative dielectric

Explanation: The force summing device is used to change the distance between the parallel plates of capacitor thereby changing the capacitance. Similarly, the inductance value can also be changed in the stable LC oscillator.

9. The change in the oscillator frequency caused by the externally applied force can be measured by an ________
a) Electrical counter
b) Electronic counter
c) Chemical counter
d) Mechanical counter

Explanation: The change in the oscillator frequency caused by the externally applied force can be measured by an electronic counter. This transducer measures both the static and dynamic phenomena and its telemetry system.

10. If the metal conductor is stretched then the resistance changes because of ______
a) Dimensional changes
b) Distance change
c) Change in medium
d) Change in dielectric

Explanation: If the metal conductor is stretched then the resistance changes because of dimensional changes. It means the change in length and the cross sectional area results in the change in resistivity.

Sanfoundry Global Education & Learning Series – Basic Electronics Engineering.

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