Voltage is how much force the electrons are being pushed. Current is how many are flowing. So If I increase the voltage, means I increase the pressure and current will increase too.
Exactly, if it helps my analogies are :
- I think of electrons as a gas.
- I think of a large resistance as a thin pipe, and a small resistance as a thick pipe, which makes it easier or harder for the current to flow.
- I think of a capacitor as a membrane in a pipe; if pressure (voltage) is increased on one side the membrane bulges and the pressure must also change on the other side. A larger capacitor means a larger area membrane or a softer material. A smaller capacitor means a smaller area membrane or a harder material.
- I think of an inductor as lots of fans in a pipe. If current flows the fans spin, and if no more current is forced through, the fans continue to spin for a while.
There are different kind of power supplies, those supply different currents in same voltage. They reduce current using resistance and increase using transistors. Right ?
Almost. Power supplies are normally regulated to supply either a fixed voltage or a fixed current. The regulating circuit would then adjust the other unknown quantity to whatever is necessary. What type of components do the regulation might vary but for a voltage source it is often the case that transistors supply more current when neccessary and a resistance draws a smaller current to get a stable regulation circuit.
- I would think of a transistor as an adjustable resistor. In the pipe/membrane analogy, think of a hose that you can squeeze to make the pipe thinner.
Now the confusion part, what I think is that how much current will be pulled from power supply is depend on the device that need the electricity. And if device pulls more current than power supply can push, power supply will heat up and blow.
Right. That can happen. It doesn't have to happen, but it could. And often the heat causes something else than an explosion.
My actual question is, can we force an electronic device to use more current if more current is being pushed from power supply ? If yes, then how come a fan only takes 1A while air conditioner takes 10A on same power supply. Why fan is not blowing up ?
The answer is yes or no, depending on the circuit. Like the voltage sources, most electronic circuits are designed to operate on either fixed conditions for voltage, or fixed conditions for current. If you increase the quantitity that was seen as fixed in the design the device will usually draw more power and heat up until it (...whatever happens...). Now some electronics include their own power supply regulation, usually in forms of a transformer that converts an expected input to an output, and it can provide some overload protection if the input exceeds maximum values. In the case of overload protection you would just shunt the extra power and the actual part that does something useful would hardly see any change in the available power... at least until the overload protection itself melts.
In the case of your USB phone charger you are looking at a (more or less) fixed voltage source. In one case it is limited to supplying 0-200mA, and in the other case it is limited to supply 0-1500mA. If the phone is designed in a way so it can detect how many amps are available, then it can regulate itself how many amps are used for charging (at a safe rate for the proprietary battery, and ratings of internal components). Keeping things safe for the charger might be more tricky, but usually (I imagine) by sensing the input temperature, and the voltage vs current draw, you would have a pretty good idea if you are within safe limits. Anyway, if you draw too much current and the supply couldn't handle it people would normally not think "it was the phone's fault", the would say that was the charger, and get a new one with the right specs. If you were to swap the charger with one that supplies more voltage, overload protection in the phone would likely just shunt that until something melts.