Question 3.38: A coil of inductance 1 mH and resistance 50 Ω connected in s......

Resonant frequency,            \mathrm{f}_0=\frac{1}{2 \pi \sqrt{\mathrm{LC}}}, \mathrm{f}_0=50 \mathrm{~Hz} \text { (given) }

or,                   \mathrm{LC}=\frac{1}{\left(2 \pi \mathrm{f}_0\right)^2}

or,                      \mathrm{C}=\frac{1}{\left(2 \pi \mathrm{f}_0\right)^2 \mathrm{~L}}=\frac{1}{(2 \times 3.14 \times 50)^2 \times 1 \times 10^{-3}}

= 0.0101 F

At resonance,                   \mathrm{X}_{\mathrm{L}}=\mathrm{X}_{\mathrm{C}}, \mathrm{Z}=\mathrm{R}

Voltage drop across R = Supply voltage = \mathrm{I}_{\mathrm{m}} \mathrm{R}=\mathrm{I}_0 \mathrm{R}

Thus, the applied voltage = 5 \times 50=250 \mathrm{~V}