Lecture-08#Series and Parallel combination of Resistances,By N.K.Nishad Sir

Resistance can be joined to each other by two ways:
1. Series combination
2. Parallel combination

SERIES COMBINATION:-

Characteristics:
1. If different resistances are joined with each other such that there is only one path for the flow of electric current then the combination of such resistances is called Series Combination.
2. In series combination current through each resistor is constant.
3. In series combination Potential difference across each resistor is different depending upon the value of resistance.
4. Equivalent resistance of circuit is equal to the sum of individual resistances.

Re = R1 + R2 + R3 + R4 + …………….. Rn

DISADVANTAGE:-

If one component is fused, then the other components of circuit will not function.


EQUIVALENT RESISTANCE IN SERIES COMBINATION

Consider three resistances R1, R2, & R3 connected in series combination with a power supply of voltage.
Potential difference of each resistor is V1, V2, & V3 respectively. Let electric current I is passing through the circuit.
Now
V = V1 + V2 + V3
According to Ohm’s law V = IR
thus
IRe = IR1 + IR2 + IR3
IRe = I(R1 + R2 + R3)
IRe/I = R1 + R2 + R3
Re = R1 + R2 + R3
This shows that in series combination equivalent resistance of circuit is always greater than individual resistances.

PARALLEL COMBINATION:-

Characteristics:
1. If there are more than one path for the flow of current in a circuit then the combination of resistances is called Parallel Combination.
2. In parallel combination current through each resistor is different.
3. Potential difference across each resistor is constant.
4. Equivalent resistance of circuit is always less than either of the resistances included in the circuit.

ADVANTAGE:-

In parallel combination of resistors, if one component of circuit (resistor) is damaged then rest of the component of the circuit will perform their work without any disturbance. It is due to the presence of more than paths for the flow of electric current.

EQUIVALENT RESISTANCE IN PARALLEL COMBINATION

Consider three resistances R1 , R2 & R3 connected in parallel combination with a power supply of voltage V.
Now
I = I1 + I2 + I3
according to Ohm’s law
V/R = I
Therefore,
V/Re = V/R1 + V/R2 + V/R3
V/Re = V(1/R1 + 1/R2 + 1/R3)
V/ReV = 1/R1 + 1/R2 + 1/R3
OR


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

link-

Series and parallel combination of resistances,Basic concept of current electricity,Series combination of resistance,Parallel combination of resistances,Ohm's law,