Question

Three resistors each of $2\Omega$ are connected together so that their total resistance is $3\Omega$. Which combination is correct ?

• A. two series with one in parallel.
• B. all are in series
• C. all are in parallel
• D. two parallel with one in series

Answer 1

Answer: (D)

two parallel with one in series

In this case, for the total resistance to be 3 ohms neither the series or parallel connection can be used but a combination of both is used.
The first two resistors are connected in parallel and the third resistor is connected in series with the first two resistors. Below diagram represents the above mentioned connection type. The resistances connected in parallel have a resistance given as $\frac{1}{2}+\frac{1}{2}=\frac{1}{1}=1ohm$.
This combined resistance when connected in series with third resistor of 2 ohms gives a total resistance of 2+1 = 3 ohms.
Hence, 2 resistors in parallel connection and 1 resistor in series connection with them gives a total of 3 ohms resistance.