Two or more elements are in series if they are cascaded or connected sequentially and consequently carry the same current.
The equivalent resistances of any number of resistors connected in series is the sum of the individual resistances.
Three resistances R1, R2, R3 are connected in series. The current passing through all the elements connected in series is same, I.
In the above figure1, according to KVL, sum of voltage drops in a closed loop is zero
Vs - V1 - V2 - V3 = 0 (V1,V2,V3 are drop across R1,R2,R3)
Vs = IR1 + IR2 + IR3 = I (R1 + R2 + R3) ..................(1)
In figure2, Vs = IReq .............(2)
From equations (1) and (2) Req = R1 + R2 + R3
Therefore voltage applied divides across the series connected elements.
Applications of Series Circuits :
1. Decorative serial sets, number of bulbs with low voltage ratings connected in series across existing rated voltage.
2. Voltage distribution or tapping
