An inductive proximity sensor uses the principle of .... to sense the presence of a metallic object.

• A. Induction
• B. Capacitance
• C. Ultrasonic
• D. Optics

Answer: (A)

This question tests understanding that an inductive proximity sensor detects metal through electromagnetic induction. The sensor has a coil that emits a high-frequency magnetic field. When a metallic object comes near, eddy currents are induced in the metal, creating a secondary magnetic field that alters the coil’s impedance. The sensor detects this change and signals the presence of metal.

Capacitance-based sensing detects changes in dielectric properties rather than metal presence; ultrasonic sensing uses reflected sound waves to measure distance; optics detects light transmission or reflection. These other methods don’t rely on the magnetic- field interaction with metal that inductive sensors use.