There simple rules for series and parallel circuits.
For the series circuits we have the following rules:
1)The same current flows through each part of a series circuit.(I = I1 = I2 = I3)
2)The total resistance of a series circuit is equal to the sum of individual resistances.(Req = R1 + R2 + R3)
3)The voltage applied to a series circuit is equal to the sum of the individual voltage drops.(V = V1 + V2 + V3)
For the parallel circuits we have the following rules:
1)Voltage is the same across each component of the parallel circuit.(: V = V1 = V2 = V3)
2)The sum of the currents through each path is equal to the total current that flows from the source.( I = I1 + I2 + I3)
3)The total resistance is equal to the sum of the reciprocal value of individual resistors in the circuit.
The x region represents the series circuit. The y region represents a combination of series and parallel circuit. This means that for y region we can apply laws for both series and parallel circuits.
So, all the equation can be applied to the y region.
However, not all equation can be applied to the x region. We can apply following equation to the x region:
1)I = I1 = I2 = I3
2) V = V1 + V2 + V3
3)Req = R1 + R2 + R3
