High School

The oscillator of a 98.3-MHz FM station has an inductance of [tex]2.8 \, \mu H[/tex]. What value must the capacitance be?

Answer :

The capacitance for the LC circuit with a frequency of 98.3 MHz FM station and an inductance of 2.8 µH is approximately 1.898 pF.

To determine the required capacitance value for an LC circuit that resonates at a specific frequency, we use the resonant frequency formula:

Formula:

f = 1 / (2π√(L × C))

Where:

f is the resonant frequency in hertz (Hz)L is the inductance in henries (H)C is the capacitance in farads (F)

Step-by-step Solution:

  • Convert the units for inductance and frequency:

Inductance (L): 2.8 µH = 2.8 x 10⁻⁶ H.

Frequency (f): 98.3 MHz = 98.3 x 10⁶ Hz

  • Rearrange the resonant frequency formula to solve for capacitance (C):

C= 1/[4π²f²L]

  • Plug in the values:

C = 1 / [ 4 × (π²) × (98.3 x 10⁶)²× (2.8 x 10⁻⁶) ].

C ≈ 1 / [ 4 × 9.8696 × 9.65689 × 10¹⁵ × 2.8 × 10⁻⁶ ].

C ≈ 1.898 x 10⁻¹²F.