When a circuit is in series, the voltage is shared and the current remains constant when components are added to the circuit.
When a circuit is in parallel, the voltage remains constant and the current is shared when components are added to the circuit.
Kirchhoff's Second Law states that the sum of the e.m.f's is equal to the sum of the p.d's around the same loop in a circuit. This is because of a conservation of energy: energy cannot be created or destroyed, so it must be used up within a circuit.
All sources of e.m.f. have internal resistance. For example, a battery has internal resistance due to the chemicals inside of it. In a power supply, it would be the wires and components within it.
The terminal p.d. is the p.d. across the load (external) resistance. The terminal…