How to find supply frequency of an AC circuit

Click For Summary
SUMMARY

The discussion focuses on calculating the supply frequency of an AC circuit consisting of a 100-ohm resistor and a 0.47 µF capacitor. The initial incorrect calculation yielded a frequency of 8465.69 Hz, which was deemed unrealistic. The correct approach involves determining the capacitive reactance (Xc) using the formula Xc = V/I, resulting in a reactance of 225.99 ohms. Substituting this value into the frequency formula F = 1/(2π * C * Xc) yields a corrected supply frequency of 1498.41 Hz.

PREREQUISITES
  • Understanding of AC circuit components, specifically resistors and capacitors.
  • Knowledge of capacitive reactance calculations.
  • Familiarity with the formula for frequency in AC circuits: F = 1/(2π * C * Xc).
  • Basic proficiency in algebra for manipulating equations.
NEXT STEPS
  • Study the concept of capacitive reactance and its role in AC circuits.
  • Learn how to derive and use the formula for frequency in AC circuits.
  • Explore the relationship between voltage, current, and impedance in parallel circuits.
  • Investigate the effects of different capacitor values on circuit frequency.
USEFUL FOR

Electrical engineering students, hobbyists working with AC circuits, and anyone involved in circuit design or analysis will benefit from this discussion.

Alan McMaster
Messages
2
Reaction score
0

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
 
Last edited by a moderator:
Physics news on Phys.org
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.
 

Similar threads

But is it the same for AC circuits?
  • · Replies 9 ·
Replies
9
Views
2K
AC supply - Signal generator - CRO in circuits
  • · Replies 9 ·
Replies
9
Views
2K
Induced EMF in a small square loop of wire at center of an AC Circuit
  • · Replies 2 ·
Replies
2
Views
2K
AC circuit, voltage and frequency problem
  • · Replies 10 ·
Replies
10
Views
2K
Why don't voltages add up numerically in an LCR AC circuit?
  • · Replies 5 ·
Replies
5
Views
3K
Rlc circuit with ac current source
  • · Replies 4 ·
Replies
4
Views
3K
Calculating the Flash Frequency in a Neon Lamp Circuit
  • · Replies 7 ·
Replies
7
Views
3K
Width of Resonance in RLC-circuit
  • · Replies 14 ·
Replies
14
Views
3K
Solve LC and LRC Circuits Kirchhoff's Rule Problem
  • · Replies 3 ·
Replies
3
Views
2K
Finding frequency of an AC current sin wave?
  • · Replies 6 ·
Replies
6
Views
4K