# AC Circuits: Signal Speed & Wavelength Calculation

• EvLer
In summary, an AC circuit will oscillate at a certain frequency, and you can use this information to figure out the wavelength and speed of the signal. This means that the signal does not always travel at the speed of light, but can potentially travel at a slower speed depending on the wavelength of the signal.
EvLer
If an AC circuit has a certain frequency of oscillation, let's say undamped, i.e. first order. Then there is a way to figure out the wavelength and therefore speed of the signal? Does that mean that signal does not travel at speed of light all the time, but can potentially?

The frequency of an AC signal has nothing to do with its propagation speed.

Ok,
then does electric signal travel at speed of light?

An electrical signal will travel according to the surrounding media in a typical PC
card the speed along a track of a pulse will be quite a bit less than light speed -- look
up 'Transmission Line theory'

speed = C / sqrt(k) where C = light speed and k is the permitivitty
of the surrounding dialectric , for buried PC tracks k = 4-5
Somtimes in chips gold air spaced wires may be used to avoid delays.
rate of 15 cm per nSEc would give you some idea --- But for sine propagation if the wavelength is longer that this i.e < 1 GHz then the energy transmission rate will be less than the delay because you need to receive
cyles to be meaningful

Ray.

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If you are doing basic circuit analysis, you can assume your circuits are ideal, and analyze them as though the described situations take effect instantaneously.

That is you can make this assumption since the signals travel at NEAR the speed of light--- so if the system is physically small the electric signals move through it fast enough so that you can consider them to affect every point in the system simultaneously. You would do well to know that a system that is small enough is called a lumped parameter system.

In circuit theory, we just assume this is true... however in electromagnetic field theory, we cannot assume this, and you will learn this in your future EE courses in applied EM and antenna theory--- should you choose to go that route in your studies.

Ooooh, thanks. I was wondering about lumped circuits...

## 1. What is the formula for calculating signal speed in an AC circuit?

The formula for calculating signal speed in an AC circuit is v = f * λ, where v is the speed of the signal in meters per second, f is the frequency of the signal in hertz, and λ is the wavelength of the signal in meters.

## 2. How do you calculate the wavelength of a signal in an AC circuit?

The wavelength of a signal in an AC circuit can be calculated using the formula λ = v / f, where λ is the wavelength in meters, v is the speed of the signal in meters per second, and f is the frequency of the signal in hertz.

## 3. What is the relationship between signal speed and wavelength in an AC circuit?

The relationship between signal speed and wavelength in an AC circuit is inverse. This means that as the speed of the signal increases, the wavelength decreases, and vice versa. This is due to the fact that the speed of the signal is directly proportional to its frequency, and inversely proportional to its wavelength.

## 4. How is signal speed affected by the medium in an AC circuit?

The speed of a signal in an AC circuit is affected by the properties of the medium it travels through. In general, the speed of the signal is slower in a medium with a higher density, and faster in a medium with a lower density. Additionally, electromagnetic signals travel faster in vacuum compared to other mediums.

## 5. Can the speed of a signal in an AC circuit be greater than the speed of light?

No, the speed of a signal in an AC circuit cannot be greater than the speed of light. The speed of light, also known as the speed of electromagnetic waves in a vacuum, is the fastest possible speed in the universe. The speed of any signal in an AC circuit will always be slower than the speed of light.

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