Kirchhoff's Voltage Law

Kirchhoff's Voltage Law (or Kirchhoff's Loop Rule) is a result of the electrostatic field being conservative. It states that the total voltage around a closed loop must be zero. If this were not the case, then when we travel around a closed loop, the voltages would be indefinite. So In Figure 1 the total voltage around loop 1 should sum to zero, as does the total voltage in loop2. Furthermore, the loop which consists of the outer part of the circuit (the path ABCD) should also sum to zero.

Figure 1 Around a closed loop, the total voltage should be zero

We can adopt the convention that potential gains (i.e. going from lower to higher potential, such as with an emf source) is taken to be positive. Potential losses (such as across a resistor) will then be negative. However, as long as you are consistent in doing your problems, you should be able to choose whichever convention you like. It is a good idea to adopt the convention used in your class.

Here are a number of simulated experiments based on Kirchoff's Laws. They are in order of increasing difficulty. Use the "back" button to return to this place.

 Experiment 1. Press here. 
Experiment 2. Press here. 
Experiment 3. Press here. 
Experiment 4. Press here. 
Experiment 5. Press here.