# AC direction change - how does electricity flow?

• matilda
In summary, electricity flows through a circuit in AC by transmitting energy through electric fields, and the concept of drift velocity is not necessary for understanding it. Additionally, in AC mains, the live and neutral wires do not switch roles, as they both carry alternating currents that flow in opposite directions.
matilda
If drift velocity of electrons changes in AC, how does electricity flow through a circuit to then lose potential energy to the devices in the circuit?

Also considering the change in direction, does that mean that the live wire and neutral wire also switch roles in AC mains? I am very confused about this.

A wire is something like a line with charge carriers and all rest world with no carriers. This is like an 1D world for electric field, even wire may have complex shape. The energy that these field carriers transfer to a positive charge q on the wire:
$$dW = dF\,dx = -E\,q\,dx$$
that mean the electric field give energy to q for all period, because E and dx change direction together.
Confusion comes for using DC terms to solve AC circuits but devices work differntial on AC or DC voltage. i.e. a capacitor has infinity resistance on DC and 1/ωC on AC, and this "resistance" differs to Ohmic resistance nature.

matilda said:
If drift velocity of electrons changes in AC, how does electricity flow through a circuit to then lose potential energy to the devices in the circuit?

Also considering the change in direction, does that mean that the live wire and neutral wire also switch roles in AC mains? I am very confused about this.

You will find electricity much easier to understand if you forget about drift velocity and analogies to massive particle kinetic and potential energies.

Imagine a person holding the ends of a rope wrapped around a remote pulley. He moves the rope back and forth, causing the axle of the pulley to heat because of friction. The person is transmitting energy to a remote location in a manner analogous to AC electricity. But the molecules in the rope are not drifting at all, nor are their kinetic or potential energies important.

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## 1. How does electricity flow in an AC circuit?

In an AC circuit, the direction of electricity flow changes rapidly. This is because AC, or alternating current, switches direction at regular intervals, usually 50 or 60 times per second depending on the frequency of the power source. This direction change allows for the efficient transmission of electricity over long distances.

## 2. What causes the direction change in AC circuits?

The direction change in AC circuits is caused by the use of an alternating power source, such as a generator or transformer. These devices use electromagnetic induction to rapidly switch the direction of the current, resulting in AC electricity.

## 3. How does electricity flow in a DC circuit?

In a DC circuit, the direction of electricity flow remains constant. This is because DC, or direct current, flows in one direction from the positive terminal of a power source to the negative terminal. This is commonly seen in batteries and electronic devices.

## 4. Why is AC preferred over DC for long distance power transmission?

AC is preferred for long distance power transmission because it is more efficient and can be easily converted to different voltages using transformers. DC, on the other hand, experiences more energy loss over long distances and requires more complex and expensive equipment for voltage conversion.

## 5. What are the advantages of the direction change in AC circuits?

The direction change in AC circuits allows for the efficient transmission of electricity over long distances, making it ideal for powering homes and businesses. It also allows for the use of transformers to adjust voltage levels, making it more versatile for different power needs. Additionally, the direction change prevents the buildup of static electricity, which can be dangerous in high-voltage systems.

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