# An AM station is broadcasting a radio wave whose frequency is 1400 kHz.

1. Jun 21, 2010

### jandominic145

1. The problem statement, all variables and given/known data
An AM station is broadcasting a radio wave whose frequency is 1400 kHz. The value of the capacitance in Figure 24.5 is 8.4 X10 -11 F. The Value of the capacitance in Figure 24.4 is 8.4X10-11 F. What must be the value of the inductance in order that this station can be tuned in the radio?

2. Relevant equations
c = f(wavelength)
S = cu

3. The attempt at a solution
but i'm not sure the fomula and i don't know how to get it

2. Jun 21, 2010

### hikaru1221

What is the natural frequency of an LC circuit oscillation?

3. Jun 21, 2010

### wwshr87

f=1400 Khz
w= 2*pi*f

The natural frequency of an LC circuit is w=(L*C)^(1/2);
solving for L and plugging in the values L=1.5385*10^-10 Henries

4. Jun 21, 2010

### vk6kro

There is a simple formula for use at radio frequencies, that uses realistic component values.

It is

L = 25330.3 / (F * F * C)

where L is in uH
C is in pF
F is in MHz

8.4 X10 -11 F is 84 pF
1400 KHz is 1.4 MHz

5. Jun 21, 2010

### vk6kro

There is a simple formula for use at radio frequencies, that uses realistic component values.

It is

L = 25330.3 / (F * F * C)

where L is in uH
C is in pF
F is in MHz

8.4 X10 -11 F is 84 pF
1400 KHz is 1.4 MHz