Skip to main content

Select preferred language from 'Translate' hidden side menu =>

Blog Navigation

By
                              Blog Navigation 
Post a Comment

Why does AC current change direction?

Image
By

Why Does AC Current Reverse Direction Periodically? Understanding Alternating Current generation, Frequency, and Working Principle of an AC generator

The answer to this question goes back to the generator where AC power is generated.

A simple voltage generator: 

Imagine a simple loop of coil is rotating between the two strong magnetic bars.

AC generator working



0 to 180 degrees,i.e. Half rotation.

You will notice that when the coil is perpendicular to the magnetic field, its output is minimum or zero due to the minimum linkage of the magnetic field. But as the coil rotates to become parallel to the magnetic field, its output increases and becomes maximum when it is parallel.

180 to 360 degrees, i.e. Full rotation.

The same cycle repeats, but now the voltage is negative. The following diagram explains it.

Generator coil rotation and corresponding sine wave output is shown

Hence, as the AC voltage reverses its polarity periodically, the load current will also change direction of flow periodically.

AC current direction:

AC current reversing direction periodically

FAQ Set:

Q1: Why does AC current reverse direction periodically?

AC (Alternating Current) reverses direction because the voltage generated by an AC generator alternates sinusoidally, causing current to flow first in one direction and then in the opposite direction.

Q2: How is AC generated?

AC is produced by rotating a coil within a magnetic field in an AC generator (alternator), inducing a voltage that changes polarity periodically according to Faraday’s law of electromagnetic induction.

Q3: What determines the frequency of AC?

The frequency (number of reversals per second) is determined by the rotational speed of the generator and the number of magnetic poles. Standard mains frequency is 50 Hz in India and 60 Hz in the USA.

Q4: What is the working principle of an AC generator?

  • A conductor (coil) rotates in a magnetic field

  • A voltage is induced across the coil

  • As the coil rotates, the induced voltage varies sinusoidally, reversing polarity each half cycle, producing alternating current

Q5: Why is AC used instead of DC for power distribution?

AC can be easily transformed to higher or lower voltages, reducing transmission losses over long distances, and its periodic reversal allows efficient operation of transformers and motors.

Q6: Does the current amplitude remain constant in AC?

No, AC voltage and current vary continuously in a sinusoidal waveform, reaching a maximum (peak) and minimum (zero) value during each cycle.

Q7: How does the periodic reversal affect electrical devices?

Devices designed for AC, like motors and transformers, rely on this reversal for efficient operation, while purely resistive loads (like heaters) are unaffected by direction changes.

More content similar to this:


If you like my answer, consider supporting us:

Gpay link



Comments

Post a Comment

Popular Posts

Blog Navigation

By
                              Blog Navigation 
Post a Comment
Read more

What happens to the energy stored in an inductor carrying a current?

By
Can the Energy Stored in an Inductor Be Used Practically? Applications, Benefits, and Real-World Examples. Why does an inductive load create sparking across contacts?  An inductor stores energy in the form of a magnetic field as long as current is flowing through it. As the current stops, the magnetic field began to collapse. Collapsing magnetic flux is also a rate of change of magnetic flux that will induce a large voltage spike (back EMF) across it. Energy stored in an Inductor:  Since this induced voltage is parallel to the inductor coil, it decays by converting it to heat across the coil resistance. During this process, the coil generates a magnetic field again due to the flow of decaying current through the coil, which results in electromagnetic interference during radio operation and sparking across open contacts. Adverse effects of stored energy in an inductor:  Can we put this back-EMF into use? Yes. Practical Use of Stored Energy in an Inductor:  Spark-ignit...
Post a Comment
Read more

What is biasing in electronics?

By
What is DC Bias Voltage used in Electronic circuits? — Definition, Importance & Practical Examples DC bias is simply a deliberate addition of a DC voltage to a (circuit) node to offset its operating voltage level. Voltage divider bias in a common emitter amplifier:  The most common and popular example of DC bias is the voltage divider bias in a common-emitter amplifier. What will happen if the DC bias is not given to the base of the above circuit? The transistor will act like a rectifier; it will amplify only the positive part of the signal, creating a distorted output that we don't want. Purpose: The purpose of the DC bias in the above circuit is to keep the base DC offset voltage sufficiently high to keep the base-to-emitter junction forward-biased all the time, considering the subtractive effect of the negative-going excursion of the AC input signal and power supply voltage variations. The typical value is 1.2V for the 12V VCC. Biasing is not always DC; it can be AC: AC bias...
Post a Comment
Read more