# Can a reed switch use a wheatstone bridge/potential divider?

## Homework Statement

Describe the principle of operation of reed switch and LDR using wheatstone bridge and potential divider arrangement

I can't find any website that says a reed switch uses a wheatstone bridge or potential divider arrangement. The only find I have found it that that a magnet if used to close and open the switch. When a magnet is moved towards the open reed switch it causes the reed pins to move together completeing the circuit. And when a magnet is applied to a closed reed switch it causes the reed pins to repel causing them to open breaking the circuit.
Because they work using a magnet I wouldn't think they would be used in a wheatstone bridge and potential divider arrangement because they are manly used for resistance devices. For example, strain gauge and LDR.

## The Attempt at a Solution

I understand how a LDR is used in a potential divider arrangement:
When the resistance of the LDR is small (When light intensity on LDR is very high),there is a small voltage drop across the LDR; this means that the output voltage (Vout) from the voltage divider is small and the transistor is switched off.
In the dark the large resistance of the LDR takes a large share of the voltage supply so Vout is large and the transistor and LED both switch on.

And in a Wheatstone bridge circuit:
In a Wheatstone bridge circuit an a resistor is replaced (normally labelled Rx) with a LDR. As light changes it causes the resistance of the LDR to change which produces a voltage across the bridge of the circuit

Last edited: