Question

Four wires meet at a junction. In two of the wires, currents and enter the junction. In one of the wires, current leaves the junction. Find the current in the fourth wire and indicate its direction.

Answer 1

Electric current is a stream of moving electrons.

The number of electrons that leave a point has to be the same as the number of electrons that arrive there.

. If they arrive and don't leave, then there has to be a way to store them there, like a capacitor or a battery.

And if they're leaving but not arriving, then there has to be a tiny factory there, manufacturing electrons and shipping them out.

The whole idea is called "Conservation of electric charge". The idea is that charge can't be created or destroyed. If charge appears, it had to come from somewhere. And if you have some that you don't want, you have to send it somewhere, because it never just disappears.

There's actually a law in electronics that covers this nicely, called Kirchhoff's current law. It says that the sum of all currents entering a single point is zero. (current coming in is positive, current going out is negative). In other words, All current In and all current Out are equal.

Answer 2

Step-by-step explanation:

Kirchoff's current law: It states that the total current entering at a junction is equal to the total current leaving at the junction. It isbased on conservation of charge.

As two current i1 and i2 is entering at the junction and i3 is leaving, so the current in forth wire is

i4 = i1 + i2 - i3