# Frequency of operation and Q factor of a coil

• Engineering
• cnh1995
In summary, the conversation discusses the Q factor and impedance of a coil after doubling the frequency. It is determined that the Q factor and impedance both double, resulting in a decrease in current and power. However, the book gives a different answer, suggesting a possible error in the book or the need to contact the publisher for clarification.
cnh1995
Homework Helper
Gold Member
Homework Statement
Select the correct option.
Relevant Equations
Q= X/R
X=wL
P=I*I*R

My reasoning:
Initial Q factor Q1= X1/R
After doubling the frequency, reactance also doubles.
So, Q2= 2(X1)/R.

Hence, Q factor doubles (option a is out).

Now, since it is mentioned that the coil has high Q factor, I assumed X >> R and hence, total impedance is approximately equal to the reactance X.
So, as frequency doubles, impedance also doubles, and current is halved.
Therefore, P decreases by 4 times.
So, d) should be the correct option.

But the book gives a) as the correct one.
Is there a mistake in my solution or is the book wrong?

Delta2
I think your analysis is correct and you're right that (d) is correct. Any way to double check the book or check with your professor?

collinsmark and cnh1995
Thanks for the confirmation.
phyzguy said:
Any way to double check the book or check with your professor?
No, I am preparing for an exam by myself. Maybe I'll write to the publisher next week.

collinsmark

## 1. What is the frequency of operation of a coil?

The frequency of operation of a coil refers to the rate at which the coil is energized and de-energized. It is typically measured in Hertz (Hz) and determines the speed at which the coil can produce an electromagnetic field.

## 2. How is the frequency of operation of a coil determined?

The frequency of operation of a coil is determined by the input voltage and the coil's inductance value. As the input voltage increases, the frequency of operation also increases. On the other hand, a higher inductance value leads to a lower frequency of operation.

## 3. What is the Q factor of a coil?

The Q factor of a coil, also known as the quality factor, is a measure of the efficiency of the coil in storing and releasing energy. It is calculated by dividing the reactance of the coil by its resistance and is a measure of how well the coil can maintain a stable frequency of operation.

## 4. How does the Q factor affect the performance of a coil?

A higher Q factor indicates a more efficient coil, meaning that it can store and release energy more effectively. This results in a more stable frequency of operation and a better overall performance of the coil.

## 5. Can the frequency of operation and Q factor of a coil be adjusted?

Yes, the frequency of operation and Q factor of a coil can be adjusted by changing the input voltage or by adding or removing elements such as capacitors or resistors in the circuit. This allows for the customization of the coil's performance for specific applications.

Replies
20
Views
3K
Replies
16
Views
1K
Replies
4
Views
3K
Replies
5
Views
3K
Replies
3
Views
2K
Replies
5
Views
2K
Replies
2
Views
3K
Replies
2
Views
1K
Replies
16
Views
2K
Replies
3
Views
1K