I am trying to learn electronics. I have read about capacitors and coils. They both seem to store energy.
I am guessing the difference is their charging and discharging characteristics?
What are the differences and how are they used?
Think of capacitors as springs. They store up charge and hold it, just as a spring stores kinetic energy as potential energy.
Think of coils as masses in the electrical circuit. They initially resist changes in current but then give way to overwhelming opinion.
Capacitors block DC and pass AC with an impedance that decreases with increasing frequency.
Inductors (coils) pass DC and attenuate AC with an impedance that increases with increasing frequency.
Using an analogy with pumed water:
Think of a DC loop circuit as a horizontal loop of pipe, containing water. Your e.m.f source (battery or whatever) is a pump pushing water around the pipe. Wires are large diameter pipes, resistors are sections of small diameter pipe.
A capacitor can be thought of as a pair of deep reservoirs with walls that go higher that the loop and water levels initially the same as the loop. Hook a capacitor into the loop and the battery will draw water from one reservoir and push it into the other one. As the reservoir levels change, they create a back pressure that opposes the push of the e.m.f source, causing the flow speed (current) to fall over time. When the reservoirs reach a certain level, the back pressure is equal to the “push” of your pump and the flow stops - the capacitor is fully charged. Capacitance is analagous to the diameter of the reservoir - the bigger the capacitor, the longer it will take to charge.
With an actual capacitor in a real circuit, pressure is analagous to voltage. When you hook a capacitor up to a battery the battery pushes charge onto one side of the capacitor and pulls it off the other. This is initially rapid but slows down as the charge imbalance creates an increasing voltage in opposition to that of the battery.
An inductor is more like a big heavy flywheel connected to a paddlewheel that blocks the flow of water. Switch your “pump” on and the current is initially slow, as the paddlewheel starts to move, but eventually the current will build and reach the same level as if the inductor wasn’t there, with the paddlewheel flying round. However, that flywheel stores energy. If you bypass the pump with a pipe and switch it off, the inductor will continue to push the water around the circuit for a time, the current gradually dropping as the flywheel winds down.
As to how they are used - that is an enormous question! I’ll give an example:
A capacitor can be used for smoothing a “ripply” voltage. Suppose you had a battery that supplied current in little pulses, and you hooked it to an LED. It would give out a flickering light. If you hook a big capacitor across such a battery, (in parallel with the LED)it acts as a charge storer and maintains the voltage during the gaps in that supplied by the battery. While such lousy batteries don’t generally exist, something similar happens when AC is turned to DC. I have a couple of radios that continue to run if you flick the plug socket switch on and off.