The series circuit rules show how to apply Ohm's law when the circuit has more than one device receiving electrical energy.
It will also help us see how the current, the resistance, and the voltage change in the circuit. Here is an example of a series circuit. The circuit has 1 switch (green), 1 voltage source of 12 volts, and 3 resistors.
Simply put, the current cannot "make choices" as to where it would go. If the current can either go this way or that way, then the circuit is not in series.
Look carefully at the circuit above and you will see that the current has to go through the path it is in. This fact leads us to Rule #1.Let I be the current going through the circuit
This series circuit has 3 resistors. Recall that a resistor is a device that resists the flow of current. Does it make sense to you that the current will be resisted by all 3 resistors? It will indeed!
For example, to find the total resistance for our circuit above, just add 1, 2, and 3.
Total resistance = 1 + 2 + 3 = 6 Ohms.
We can now use Ohm's law to find the intensity of the current flowing through the circuit.
Whenever the current go through a device, a voltage drop or potential difference occurs because of the resistor in that device. It simply means that the voltage in that device will not be the same as the voltage source.Voltageacross 1 Ohm resistor = R × I = 1 × 2 = 2 volts
From this, there is an important observation we need to make.
Notice that 12 volts = 2 + 4 + 6Let V be the voltage at the source
The series circuit rules can be summarized and generalized as follow:Let I be the current going through the circuit