Resistors in series

When two or more resistors are joined in series, then their total resistance is given by the formula-

RS = R1 + R2 + R3

The current will remain the same through all resistors. Total voltage is given by-

V = V1 + V2 + V3
Voltage across each resistor is given as –
V1 = lR1
V2 = lR2 [V1 + V2 + V3 = V]
V3 = lR3V = lR
V = lR1 + lR2 + lR3
lR = l(R1+ R2 + R3)
R = R1 + R2 + R3

Resistors in parallel
In this case, voltage is the same across each resistor and is equal to the applied voltage. The total current is given as-

V/R = V/R1 + V/R2 + V/R3
1/Rp = 1/R1 + 1/R2 + 1/R3

Advantages of Parallel Combination over Series Combination
If one component fails in a series combination, then the complete circuit is broken and no component can work properly. Different appliances need different currents.