Electricity

Kirchhaff's first law.

The sum of the currents entering any point in a circuit is equal to the sum of the currents leaving that same point.

ΣIin = ΣIout

Kirchhaff's second law.

The sum of the e.m.f.s around any loop in a circuit is equal to the sum of the p.d.s around the loop.

 ΣE = ΣV