Electricity - Kirchhoff's Laws

Question 1

What are Kirchhoff’s Laws?
(What do Kirchhoff’s laws quantify?)
(What is Kirchhoff’s first law?)
(What is Kirchhoff’s second law?)

Answer 1

• Kirchhoff’s laws quantify how current flows through a circuit and how voltage varies around a loop in a circuit
• Kirchhoff’s Current Law (1st law) states that the current flowing into a node (or a junction) must be equal to the current flowing out of it. This is a consequence of charge conservation.
• Kirchhoff’s Voltage Law (2nd law) states that in any complete loop within a circuit, the sum of all voltages across components which supply electrical energy (such as cells or generators) must equal the sum of all voltages across the other components in the same loop. This law is a consequence of both charge conservation and the conservation of energy.

Question 2

Kirchhoff’s Current Law

Answer 2

• Current flow in circuits occur when charge carriers travel around the circuit.
• Current is defined as the rate at which this charge passes any point in the circuit.
• Current flowing into a point must be the same as the current flowing out of that point.

Question 3

Kirchhoff’s Voltage Law

Answer 3

• As charge carriers flowing through a circuit pass through a component, they either gain or lose electrical energy, depending upon the component. This is due to the fact that work is done on or by them as a result of the electrical forces inside the components.
• The total work done must equal the total work done by the charge carrier in other components by the time it has gone round the circuit once.
• This means that the sum of all potential differences across the components involved in a circuit’s loop must be zero.