So basically I’ve looked at the wiring of some bulbs and other applicants around me and I’ve observed that some applicants have just two thin wires connected to it some have 10 thin wires, other have two thick wires etc etc.. what are the differences basically?
In: Engineering
Wire size, more specifically its diameter, determines how much current the wire can carry before it heats up too much and melts. An LED draws very little current, so very thin wires are sufficient. A hair dryers draws quite a bit of current, so requires much thicker wire.
The short of the size is basically how hot you’re allowing the wire to get to prevent a catastrophic failure (too hot = fire, wire failure), while the stranded/solid choice is done for different reasons (solid retains its shape easier, stranded bends easier for example).
The long of it:
As with most things, moving particles in the wire experience some friction which ends up as heat. With electricity this is a function of the amount of current going through the wire the length it has to be transported through* and the cross section of the wire (it’s size or gauge).
Since the location of the thing that needs power (relative to the source of that power) and the electrical needs of the device are things you generally cannot change, the gauge is used to ensure safety.
Less cable = less weight and also less copper, which means cheaper in many ways.
Take an LED for example. A fairly bright single LED will consume ~20 mA at 1.6V and is often very close to a source of power. As a result, you can get away with using a very small cable to power it. A 120W incandescent bulb will need 1000mA for about 15 metres from the breaker panel so it’ll need thicker wires. If you’ve seen the LED at the front of an Apple TV let me tell ya: I’ve had the misfortune of breaking such a wire and I’m not exaggerating when I say it’s smaller than thin hair. Getting it to work again was a bit of fun. It doesn’t need to be any larger than that but you can always choose to put a bigger one at an extra cost.
As for stranded vs solid: a stranded wire is easier to bend, and is not subjected to a spurious current called Eddy current like a solid cable, so they’re better for signals such as Ethernet cables, while a solid cable is better suited for applications where you’re expecting the wire won’t move but you don’t care about the quality of the current going through it.
*alternate current is a bit more complex, but direct current is more susceptible to distance
The guy under answered the thickness question, when we use many wires it’s because we use them for connecting devices that communicates, like in Ethernet cable we have 2 twisted pairs, many cables use more then one line because you may want to sand not only power but data
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