Which component is used as a simple, low-cost switch in magnetic sensing?

• A. Reed Switch
• B. Capacitive Sensor
• C. Inductive Sensor
• D. Optical Sensor

Answer: (A)

When you want a switch that responds directly to a magnetic field, a reed switch is the simplest and most cost-effective option. It’s a small glass-encapsulated device with two ferromagnetic reeds that touch together to close the circuit when a magnet is brought near. Because it’s just a mechanical contact that can be actuated by magnet presence, it doesn’t require its own power to operate and is inexpensive and compact, which is ideal for low-cost magnetic sensing applications.

Other sensor types don’t fit this use as cleanly. Capacitive sensors detect changes in dielectric surroundings, not magnetic fields. Inductive sensors sense metal targets through changes in inductance and usually require more electronics and cost. Optical sensors rely on light paths and are activated by image or light changes, not magnetism. So for a simple, low-cost magnetically actuated switch, the reed switch is the best fit.