How is a reed switch used to charge/discharge a capacitor


Ok, so there's no way to disguise this; I admit this is a question I've been set for homework but I can't find a full answer to.

I know that, in brief, a reed switch consists of two metal contacts inside a glass tube and can be operated by a magnetic field, and I've seen lots of experiments involving capacitors and reed switches (most of which also involve a signal generator), but I cannot seem to find any explanations.

Could somebody explain to me how you can charge and discharge a capacitor using a reed switch and the physics behind it please?

By the way, I am studying Physics at A2 level.

Best Answer

To charge the capacitor, a normally open reed switch is interposed between a voltage source and the capacitor, then the reed switch is exposed to a magnetic field of sufficient intensity that it causes the contacts to attract each other until they touch, allowing charge to flow from the voltage source, through the made contacts, and into the capacitor.

Once the capacitor is charged, the magnetic field can be removed, allowing the contacts to open and the charge in the capacitor to remain there.

In order to discharge the capacitor, the voltage source is removed and replaced with a load of some kind, the reed switch energized once again by the magnetic field and, when the contacts make, the charge stored in the capacitor will flow into the load, discharging the capacitor.