Current and voltage in AC

In summary, the conversation discusses the relationship between voltage and current in AC circuits. In AC current, the electrons move back and forth without ever reaching the source of the voltage. However, the energy to move the electrons is provided by the turbine, similar to how energy is transferred in waves on a string or by rubbing hands together. This is represented by the equation Positive Voltage * Positive Current = Positive Power.
  • #1
I am sorry if this may seem like a beginner question (which I am not) but the I find the best way to learn something is to understand it from it's most basic components or operations first. In this spirit I have a question regarding the relationship between voltage and current in AC circuits. Voltage is defined as the energy required to move an electric charge from point A to point B (divided by the magnitude of the charge). In DC current when two wires are connected to the leads of a battery, the electron flow (not to confuse with the conventional current) is from the negative lead, or the most negative voltage to the positive lead or the most positive voltage. Along the way, the electrons move through the wire and dissipate their energy (voltage or eV) in the components they encounter in the circuit so when they arrive at the positive lead they will have no more energy or voltage. This part is clear. The thing I don't understand is in AC current. AC current being the come and go of electrons in the wire, they actually always end up in the position they started. I was wondering then, where does the voltage to move the electrons come from. In other words how is the voltage from the turbine at the electrical central transferred to the electrons present in the wall socket of my house since these electrons basically never reach the turbine. They seem to move forward and lose energy and then coming back losing some more in the other direction without recuperating it anywhere.

Thank you

I am sorry if it is not clear enough don't hesitate to tell me.
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  • #2
Compare AC with waves on a string.Particles in string oscillate about their position but net displacement in a time period their net displacement is zero.Yet your energy gets transferred across string and even released if there is some damping(just as resistance in case of DC or AC circuits). However the energy to oscillate the string is given by you or the oscillator.Similarly the energy to oscillate electrons about their mean position is given by the turbine.
  • #3
What a silly contraption a bicycle is. All you do is move your legs up and down, around in a circle, how you you possibly get anywhere?


Think about that a little bit, and you might get it.

Here's another one. Press your hands together, and rub them back and forth. You're movig your hands back and forth in opposite directions, and yet you generate heat! They end up right back where they started, and yet work has been done.

The final clue...

Positive Voltage * Positive Current = Positive Power

Negative Voltage * Negative Current = Positive Power

Does it make sense now?

1. What is the difference between current and voltage in AC?

Current refers to the flow of electric charge through a circuit, while voltage is the force that drives this flow. In AC (alternating current) circuits, the direction of current and voltage constantly changes, resulting in a back-and-forth flow of electricity.

2. How is current and voltage measured in AC circuits?

Current is measured in amperes (A) using an ammeter, while voltage is measured in volts (V) using a voltmeter. These instruments can be connected in series or parallel with the circuit to measure the current and voltage respectively.

3. What is the relationship between current and voltage in AC circuits?

Ohm's Law states that the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance. In AC circuits, this relationship is described by the impedance, which takes into account the resistance, inductance, and capacitance of the circuit.

4. Can current and voltage in AC circuits be out of phase?

Yes, in AC circuits, the current and voltage may be out of phase with each other. This means that they do not reach their maximum and minimum values at the same time. This phase difference is caused by the reactive components, such as inductors and capacitors, in the circuit.

5. Why is alternating current used instead of direct current?

Alternating current is used for long-distance power transmission because it can be easily transformed to different voltages using transformers. It is also more efficient for powering devices that require high voltages, such as electric motors. Direct current, on the other hand, is suitable for low-power devices and is commonly used in batteries.

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