• qaisarpk1

MemberAug 13, 2010

## What is the Relationship Between Frequency and Power?

In most basic terms, frequency and power are two distinct properties of an electrical signal or system.

Frequency refers to the rate at which a signal or an electrical wave oscillates, generally measured in cycles per second, or hertz (Hz).

It can apply to both direct current (DC) and alternating current (AC) systems, but it is primarily important in AC systems.

AC signals can have various forms like sinusoidal, square, or triangular waveforms, and frequency measures how quickly these waveforms repeat.

Power, on the other hand, is the rate at which energy is transferred, used, or transformed.

In an electrical system, it is typically measured in watts (W) and it is given by the product of voltage and current (P = V I). In an AC system, due to the presence of phase difference between voltage and current, the power factor comes into play and the equation becomes P = V I * cos(ϴ) where ϴ is the phase difference between voltage and current.

Now, how are frequency and power related in an electrical or electronic system?

1. Power Transmission: In electrical power systems, power is transmitted at very high voltages and low currents to reduce line losses. These systems often operate at specific, standardized frequencies (like 50 or 60 Hz) because the equipment is designed for optimal operation at these frequencies. Changing the frequency can impact the power that equipment can handle or produce, possibly causing equipment to malfunction or become less efficient.

2. Resonant Frequency and Power in Circuits: In AC circuits with inductors and capacitors, there's a specific frequency at which the circuit becomes resonant (the resonant frequency), which means it's able to store and transfer energy most efficiently. At this frequency, the impedance of the circuit is at a minimum (in a series resonant circuit) or maximum (in a parallel resonant circuit), which results in maximum power transfer.

3. Power Electronics and Switching Losses: In power electronics, devices like inverters and converters often switch between different states to control power flow. The frequency at which they switch can significantly impact the power loss in these devices. Higher switching frequencies may allow for more compact and efficient designs but can also increase switching losses, reducing overall efficiency.

4. Frequency and Electromagnetic Interference (EMI): Higher frequencies can result in increased EMI, which can affect the proper operation of electronic devices and reduce their power efficiency. Therefore, it's crucial to manage and mitigate EMI in high-frequency electronics.

5. Frequency Response of Electronic Systems: In many electronic systems, such as amplifiers or filters, the relationship between frequency and power is described by the system's frequency response. This response shows how the power output of the system changes with frequency. In many cases, the system will output maximum power at one specific frequency, with power output decreasing at higher or lower frequencies.

It's important to note that while frequency can affect power in these and other ways, they are not directly proportional or linked by a simple equation in the general case.

The relationship between frequency and power in an electrical or electronic system depends on many factors, including the characteristics of the components and the configuration of the system.

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Replies
• MemberAug 13, 2010

I think you know that power is directly proportional to energy.
E=h*(new);
where new represent frequency of the signals.
so you can say that power is directly proportional to frequency.
.
frequency is inversely proportional to time so and time is directly proportional to distance.
So with low frequency you can travel more distance.
low frequency->more time->>more distance.
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• MemberAug 13, 2010

In terms of electricity there is no relationship. Electrical power is simply the product of the current and the voltage.
The lower the current is the less resistance there is to the current flowing through the conductor. That is why electrical power is transformed to high voltage (low current) when it is transmitted over long distances. This is a property of an electromagnetic wave i.e. wave particle duality.

The frequency of light does however affect the energy of the light wave viz. E = hf where h is Planck's constant and f is the frequency. Since c = fl, f = c/l. This simply implies that the frequency is a way to describe the rate of wave formation i.e. so may times per second and so we can say that the energy of a light packet is equal to some number multiplied by how many times per second the wave regenerates.
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• MemberAug 14, 2010

its fine mohit .....
as u said that the lower frequncy travel more distance then why we modulate low freq signal on higher frequencies ....
kindly explain one more thing that why we use higher freq in satellite comm instead of lower freq as lower freq travel more distance....
thanx....
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• MemberAug 14, 2010

Could someone please formulate a mathematical relationship and provide an answer to the following question:

A nano-car travels on the edge of a light wave i.e. in a sinusoidal pattern. Remember that the speed of light is constant and hence our little car has to travel at some theoretical speed greater than c[/c]. The little car first travels on a wave with wave lenth l and then on a second light wave with a frequency double that of the first wave.

Q: on which wave does the little car travel the furthest distance in one time period.
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• MemberAug 15, 2010

qaisarpk1
its fine mohit .....
as u said that the lower frequncy travel more distance then why we modulate low freq signal on higher frequencies ....
kindly explain one more thing that why we use higher freq in satellite comm instead of lower freq as lower freq travel more distance....
thanx....
Ah !!! Unfortunately, lower the frequency greater is the antenna size required to radiate that frequency. It follows the lambda/4 relationship.

- Karthik
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• MemberAug 25, 2010

I have posted something in it which may interest you.
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• MemberAug 26, 2010

Ah, how did I miss this??

Actually, lower the frequency, LESSER is the distance it can travel before it gets attenuated too much, or get corrupted by noise.

Higher the frequency, lesser is the attenuation. Which means, higher the frequency, greater is the distance which the wave can reach with reasonable attenuation levels.

This is the reason we modulate baseband signals to high frequencies in radio communication, It's also the reason for very high frequencies in case of satellite communications.
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• MemberAug 10, 2012

silverscorpion you got the concepts reversed there.. Lower the frequency LARGER is the distance it can travel.. and vice versa.. The reason for high frequency communication in satellites is that we can't have large antennas hanging around in space..
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• MemberMay 18, 2013

well mr. silver i have a question,
if signal attenuation is more in low frequency signal then why there is more attenuation in 30/20 GHz band in satellite communication as compared to 6/4 GHz band.
Thank You
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• MemberMay 20, 2013

vikash_pandey
well mr. silver i have a question,
if signal attenuation is more in low frequency signal then why there is more attenuation in 30/20 GHz band in satellite communication as compared to 6/4 GHz band.
Thank You
Satellite are not very close to earth and air media travelled by these waves have ions(ionosphere) and so there is no ideally unity permittivity

That tells us the actual reason
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• MemberNov 5, 2015

One persons say attenuation is independent of frequency in free space ,.... then says lower frequency higher distance, again challenged by someone please we get confused.
It seems everybody is correct in their own explanation. But totally confused
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• MemberNov 5, 2015

lord_slayer
silverscorpion you got the concepts reversed there.. Lower the frequency LARGER is the distance it can travel.. and vice versa.. The reason for high frequency communication in satellites is that we can't have large antennas hanging around in space..
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• MemberNov 5, 2015

I am working in GPS. we receive satellite signals at 1575.42MHz from thousand of miles distance . So my question is that whether there is no attenuation in signal between receiver and satellite.
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• MemberNov 9, 2015

SATINATH DEBNATH
I am working in GPS. we receive satellite signals at 1575.42MHz from thousand of miles distance . So my question is that whether there is no attenuation in signal between receiver and satellite.
Hey buddy 1575.42MHz=(approx) 1.5 GHz.

In the GHz region there are certain bands of frequencies that are affected very less by Atmosphere and water particles in air. You can refer any microwave books for more details on this.

And I am not clear of what you say here
I am working in GPS. we receive satellite signals at 1575.42MHz from thousand of miles distance .
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