Why cant the current from the socket turn on the air conditioner but the current in capacitor to turn it on ?
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Electric motors are interesting in that they draw more current the slower they are turning. A motor that draws 5 amps at top speed might draw 30 amps when it is not spinning. Contrary to some other responses, it it not due to static friction, but to an effect called back emf.
Electric motors spin by putting electric current through loops of wire creating electromagnets. Through clever wiring connections, the poles of those magnets shift as the motor spins allowing for continuous rotating forces. But it turns out that the universe fights changes in magnetic fields, and the faster the motor spins the more quickly the magnetic field changes. The way that the universe fights the changing magnetic field is by producing electric voltage (this is how generators work) in the opposite direction of the applied voltage. This reversed voltage is called back electromotive force or back emf. A motor’s top speed is set by when the back emf counteracts the applied voltage. Back emf acts like a resistor, limiting the amount of current in a circuit. If the current is low, then thin wires can safely be used without overheating.
When a motor first starts up, as the motor isn’t spinning yet, there isn’t any back emf yet, therefore the effective resistance in the motor is very small, and a huge current flows through the motor. This surge only lasts until the motor is up to speed, but can be enough to blow a standard household circuit breaker. A capacitor will store energy and then give it to the motor during startup to avoid pulling excessive current from the household circuit. Once the motor is spinning, the household circuit can safely handle the load.
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