Question

A Linear Variable Differential Transformer works on the principle of

• A. Mutual Resistance
• B. Mutual Induction
• C. Mutual Capacitance
• D. Magnetic Induction

Hint:

An LVDT uses mutual induction: the primary coil’s magnetic field induces voltages in two secondary coils, and the core’s position creates a differential output proportional to displacement.

Answer 1

The Correct Option is B

Step 1: Understand the Linear Variable Differential Transformer (LVDT).
A Linear Variable Differential Transformer (LVDT) is a type of electromechanical transducer used to measure linear displacement. It consists of a primary coil, two secondary coils, and a movable ferromagnetic core. Step 2: Analyze the working principle of an LVDT.
The LVDT operates based on the principle of mutual induction.
An alternating current (AC) is applied to the primary coil, which generates a magnetic field.
This magnetic field induces voltages in the two secondary coils through mutual induction (the coupling of magnetic flux between the primary and secondary coils).
The secondary coils are wound in opposite directions, so the induced voltages are out of phase.
The movable core changes the magnetic coupling between the primary coil and each secondary coil depending on its position:
When the core is centered, the induced voltages in the secondary coils cancel out (net output is zero).
When the core moves, the coupling changes, resulting in a differential voltage output proportional to the core’s displacement.
Thus, the LVDT converts linear displacement into an electrical signal using mutual induction. Step 3: Evaluate the options.
(1) Mutual Resistance: Incorrect, as resistance is not a principle involved in LVDT operation; it deals with magnetic fields and induction. Incorrect.
(2) Mutual Induction: Correct, as the LVDT relies on mutual induction between the primary and secondary coils to generate a differential voltage based on core position. Correct.
(3) Mutual Capacitance: Incorrect, as capacitance is relevant for capacitive sensors, not LVDTs, which use magnetic fields. Incorrect.
(4) Magnetic Induction: Incorrect, as "magnetic induction" typically refers to the generation of a magnetic field or electromotive force in a single coil (Faraday’s law), whereas LVDT specifically relies on mutual induction between multiple coils. Incorrect. Step 4: Select the correct answer.
A Linear Variable Differential Transformer works on the principle of mutual induction, matching option (2).