Which of the following combinations should be selected for better turning of an LCR circuit used for communication ?

Options

A. `R = 20 Omega, L = 1.5 H, C = 35 mu F`
B. `R = 25 Omega, L = 2.5 H, C = 45 mu F`
C. `R = 15 Omega, L = 3.5 H, C = 30 mu F`
D. `R = 25 Omega, L = 1.5 H, C = 45 mu F`

Answer

C

Explanation

For better tuning of an L-C-R series circuit, used for communication , the quality factor of the circuit should be high.
The quality factor (Q) of an L-C-R circuit is given by
`Q = 1/R sqrt(L/C)`
Hence to make Q high, R should be low, C should be low and L should be high.
In the given combinations, the combination (c)
i.e. `R = 15 Omega, L = 3.5 H, C = 30 mu F`
is the most suitable combination.