0Resistance:
Resistance is the opposition that a substance offers to the flow of electric current. It is represented by the uppercase letter R.
If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behaviour of the material.
Resistance in Series Circuits:
A series circuit is a circuit in which resistors are arranged one after the other, so the current has only one path to flow. The current(I) is the same through each resistor. The total resistance of the circuit is found by simply adding up the resistance values of the individual resistors:
equivalent resistance of resistors in series : R = R1 + R2 + R3+....+Rn
where the n= number of resistors.
Example:
If R1=4Ω, R2=5Ω and R3=6Ω, then total resistance for series combination will be:
R = R1 + R2 + R3= 4+5+6=15Ω
With a 10 V battery, by V = I R the total current in the circuit is:
I = V / R = 10 / 15 = 0.6 A. The current through each resistor would be 0.6 A.
Resistance in Parallel Circuits:
A parallel circuit is a circuit in which the resistors are arranged in a parallel fashion. The current in a parallel circuit breaks up, with some current flowing through each parallel resistor and re-combining at the meeting point. The voltage across each resistor in parallel is the same.
equivalent resistance of resistors in parallel: 1 / R = 1 / R1 + 1 / R2 + 1 / R3 +...+1 / Rn
where the n= number of resistors.
Example:
If R1=4Ω, R2=5Ω and R3=6Ω, then total resistance for series combination will be:
1 / R = 1 / R1 + 1 / R2 + 1 / R3=1/ 4+1/5+1/6=37/60
therefore. R=60/37=1.62Ω
With a 10 V battery, by V = I R the total current in the circuit is:
I = V / R = 10 / 1.62 = 6.17 A. The total current would be 6.17 A.
