Understand Alternating Current: Electric Flow & Energy

In summary: TERRIBLE analogy for explaining the complexities of electricity. In summary, current is a flow of charge, alternating current is a type of current where the voltage changes with time, and voltage and current have a phase.
  • #1
mohammad_adam
24
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So I get the general idea of electricity being the flow of charge (or lack of electrons) but when it's alternating I don't quite understand what's going on. So the current is just pulsating back and forth? How do they refer to this bring the transmission of electrical energy?? Isn't it essentially not even technically "flowing"?
 
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  • #2
Are there any other things that go back and forth that can transfer energy from one place to another?
What about when you rub two sticks together to light a fire?
 
  • #3
Hmmm I guess I see what u mean, not entirely, but sort of.
 
  • #4
Is current meant to be looked at as flowing water? Flowing water which is sent down kilometers of transmission lines, allowing anyone to hook up and draw some water from it? If the analogy is appropriate, then how does AC fit in?
 
  • #5
Also, y does current (and voltage) have a phase? What does that angle represent? Is it the position of a given amplitude along a sinusoid?? I've never fully wrapped my head around that
 
  • #6
The analogy of water to current is VERY problematic and breaks down in the sense in which you are exploring electricity. Google "electron drift"
 
  • #7
mohammad_adam said:
Is current meant to be looked at as flowing water?
Not really - it is a way to hep students learn about simple electric circuits.

Flowing water which is sent down kilometers of transmission lines, allowing anyone to hook up and draw some water from it? If the analogy is appropriate, then how does AC fit in?
By analogy, the water source would be ocean waves.
But it starts to get very shaky.

mohammad_adam said:
Also, y does current (and voltage) have a phase? What does that angle represent? Is it the position of a given amplitude along a sinusoid?? I've never fully wrapped my head around that
The changes in electric potential (voltage) do not have to in sync with changes in the electric current. Why would you expect it to?

A varying voltage can be represented as the sum of sinusoids.
A sinusoid can be represented as the vertical position of the tip of an arrow turning in a circle.
http://en.wikipedia.org/wiki/Phasor

The phase angle is the angle the arrow makes to some reference direction.
In this case, the arrow represents voltage and the reference direction is the current.
 
  • #8
mohammad_adam said:
So I get the general idea of electricity being the flow of charge (or lack of electrons) but when it's alternating I don't quite understand what's going on. So the current is just pulsating back and forth? How do they refer to this bring the transmission of electrical energy?? Isn't it essentially not even technically "flowing"?

You may be leaping into the subject too far and too quickly if you really want to understand it. I suggest you read around Wiki and Hyperphysics sites. This is not a very 'intuitive' subject and you need to build up on basics first.
 
  • #9
I agree lol. I duno how I did 3 years of electrical engineering. But then I guess not too many ppl give enough of a damn to look into these things deeply, they just take things for face value, memorize a bit of this n a bit of that, and voila u got urself and engineering degree. I hope to learn more deeply than that, thanks for all the help guys, I guess I'll build up on the basics first and then return to physics forums.
 
  • #10
You did 3 years electrical engineering at college level?
I was answering at senior secondary-school level :)

Many people look into these things deeply, it's just that people interested in fundamental concepts tend not to become engineers. <ducks>

You probably want to review the basics from the physics perspective rather than the engineering one.
 
  • #11
That's very true... I guess engineering being the application of science doesn't allow room for pondering the technical nature of things down on the small scale. Its Definitely some mind blowing stuff to attempt to understand though. There's probably no better hobby on the planet.
 
  • #12
mohammad_adam said:
That's very true... I guess engineering being the application of science doesn't allow room for pondering the technical nature of things down on the small scale. Its Definitely some mind blowing stuff to attempt to understand though. There's probably no better hobby on the planet.
It's pretty much why all of us are here, yes :D
I'd go so far as to say that it is the best purpose for self-aware entities... but that's a personal philosophy.
 
  • #13
The simple example is think of the piston on an old steam loco - the piston goes back and forth and the connecting rod ( conductor - sorry for the dual rr meaning) - pushes - then pulls (2 directions) , delivering energy TO the wheels in each direction - power delivered in one direction - from the piston to the wheels. As for the water analogy - I do tend to like it for BASIC descriptions - and a closed hydraulic system can be used to demonstrate may principals.

The basic of confusion comes from thinking of ONLY current - in electrical power - we need to discuss Voltage and Current - and in AC we can mathematically represent these with vectors. so if Current is flowing in the Positive direction ), and the Voltage is Positive - it is the same direction of power flow as Current in the Negative Direction and Voltage is Negative.

As for phase - it has many meanings depending on the specifics of the discussion - for a single wave for it can be relating to apaecific point in the the wave, in power it typically details the relative angle of two waveforms - thay can be both voltages - both currents, V and I - etc.
 

1. What is alternating current (AC)?

Alternating current is a type of electrical current in which the direction of the flow of electrons periodically reverses. This means that the flow of electricity alternates back and forth, unlike direct current (DC) which flows in only one direction.

2. How is alternating current different from direct current?

As mentioned, alternating current flows in both directions while direct current only flows in one direction. Additionally, AC is typically used for long-distance transmission of electricity, while DC is commonly used for electronic devices. AC can also be converted to different voltages using a transformer, while DC cannot.

3. How is alternating current produced?

Alternating current is produced by a device called an alternator. An alternator uses a magnetic field and a coil of wire to convert mechanical energy into electrical energy. As the coil rotates, it creates a changing magnetic field, which in turn produces an alternating current.

4. What is the frequency of alternating current?

The frequency of alternating current is measured in Hertz (Hz) and represents the number of complete cycles per second. In most countries, the standard frequency for AC is 50 Hz, while in the United States and some other countries it is 60 Hz.

5. What is the role of alternating current in our daily lives?

Alternating current is the primary form of electricity used in homes and businesses. It powers our household appliances, lighting, and electronic devices. AC is also used in industries for powering machinery and equipment. Without alternating current, our modern way of life would not be possible.

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