How to find supply frequency of an AC circuit

AI Thread Summary
The discussion centers on calculating the supply frequency of an AC circuit with a 100-ohm resistor and a 0.47 µF capacitor. The initial attempt yielded an unrealistic frequency of 8465.69 Hz due to a misunderstanding of the relationship between voltage and reactance. Correcting the approach, the reactance was calculated using the capacitor's voltage and current, leading to a more plausible frequency of 1498.41 Hz. Participants emphasized the importance of using appropriate equations and understanding the units involved in the calculations. The conversation highlights the need for clarity in solving AC circuit problems.
Alan McMaster
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Homework Statement


[/B]
Parallel circuit consists of 100ohm resistor with 0.4A current, a 0.47uf capacitor with 0.177A current. Both connected across an AC supply, determine

Homework Equations


[/B]
The supply voltage
The supply frequency
Current drawn from supply
Power factor of the circuit
The Apparent power

The Attempt at a Solution


[/B]
The supply voltage is 40V.
Supply frequency is where I am stuck at the minute. I have VL=VC=XC

So VC=1/(2PiFC)
Substitute F for VC and I get VC=1/(2PiC*VC)
F= 1/(2Pi *0.47x10-6*40V)
Doing that equation I get 8465.69Hz which is crazy?

Thanks in advance Alan
 
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Hello Alan, welcome to PF :)

Do the relevant equations look like equations to you ?

I take it the 40 V follows from I = V/R, so that qualifies as an equation and you have attempted a solution (and it's OK)

Perhaps the 0.177 and the 0.47 uF plus the 40 V can lead you to a frequency -- if you have a decent equation at hand, that is. Any idea ?


PS Check out the guidelines
 
Alan McMaster said:

Homework Statement



Parallel circuit consists of 100ohm resistor with 0.4A current, a 0.47uf capacitor with 0.177A current. Both connected across an AC supply, determine[/B]

Homework Equations



The supply voltage
The supply frequency
Current drawn from supply
Power factor of the circuit
The Apparent power[/B]

The Attempt at a Solution



The supply voltage is 40V.
Supply frequency is where I am stuck at the minute. I have VL=VC=XC

So VC=1/(2PiFC)
Substitute F for VC and I get VC=1/(2PiC*VC)
F= 1/(2Pi *0.47x10-6*40V)
Doing that equation I get 8465.69Hz which is crazy?
[/B]
Thanks in advance Alan
Hello Alan,

Welcome to Physics Forums.

Voltage and reactance are not the same thing (one has units of Volts and the other Ohms). You have the potential across the capacitor (40 V) and the current though it, so you can determine the reactance...
 
This is where I am at now, Xc=V/I which is 40V/0.177A=225.99

F= 1/(2Pi * 0.47x10-6 * 225.99)= 1498.41Hz
 
Well done
 
How to calculate frequency of AC signal?
 
Sanat Mishra said:
How to calculate frequency of AC signal?
Hello Sanat, :welcome:
Please start a new thread for this question and use the homework template.
 

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