A 25 μF capacitor, a 0.10 H inductor and a 25 N resistor are connected in series with an ac source of emf ε = 310 sin 314 t. What is the frequency of AC source?

50 Hz

The correct answer is Option (3) → 50 Hz

The AC voltage is given as,

$ε=ε_0\sin(ωt)$

and $ω=314\,rad\s$ [Given]

and, $ω=2\pi v$  [v = frequency]

$v=\frac{ω}{2\pi}=\frac{314}{2×3.14}=50Hz$