Conservation of Charge & Energy in electrical Circuits

In this post, we will have some pointers on the Conservation of Charge & Energy in electrical Circuits. Charge Doesn’t ‘Leak Away’ Anywhere — it’s Conserved in electrical circuits. Energy is Conserved too.

Charge Doesn’t ‘Leak Away’ Anywhere — it’s Conserved in electrical Circuits

1) As charge flows through a circuit, it doesn’t get used up or lost.
2) This means that whatever charge flows into a junction will flow out again.
3) Since the current is the rate of flow of charge, it follows that whatever current flows into a junction is the same as the current flowing out of it.

Kirchhoff’s first law says: The total current entering a junction = the total current leaving it.

Energy is Conserved too

1) Energy is conserved (You already know that).
In electrical circuits, energy is transferred around the circuit. Energy transferred to a unit charge is e.m.f., and energy transferred from a unit charge is the potential difference.
2) In a closed loop, these two quantities (emf and potential difference) must be equal if energy is conserved (which it is).

Kirchhoff’s second law says:
The total e.m.f. around a series circuit = the sum of the p.d.s across each component. (or ε = Σ IR in symbols)

Example

If 6 coulombs of charge flow into a junction in 1 second and split in the ratio of 1:2, then see how Conservation of Charge is shown in the following figure. Also, see how the input current gets distributed at the output of the junction because of the split of the charge flow there.