Combination of resistance – In different cases, a number of resistance are connected together in an electric circuit to perform different works. This is known as the combination of resistance.
Types of connection of resistance
(i) Series connection
(ii) Parallel Connection
(i) Series Connection – In an electric circuit, a number of resistance are joined end to end consecutively so that same current flows through each, then the combination is called series connection.
In the series connection, the equivalent or total resistance (R) is given by
According to ohm’s law
VAB = IR1, VBc = IR2, VCD = IR3
Now the total potential of the circuit,
(V) = VAB + VBc + VCD
or, IR = IR1 + IR2 + IR3
or, IR = I(R1 + R2 + R3)
or, R = R1 + R2 + R3
(ii) Parallel Connection – If in an electric circuit a number of resistors are joined by placing them side by side with corresponding ends joined together so that the main current is divided among them, then the connection is called parallel connection (or combination) of resistance.
In the parallel connection, the equivalent or total resistance (R) is given by