Alternating current usually called as ac current is which changes it’s amplitude periodically with time basically it’s a sinusoidal wave which represent ac current but not in case of direct current or dc. AC current have both +ve and -ve amplitude.

Quantifying Alternating Current:

To fully describing a ac current we require a number of terms.


A cycle is part of waveform which does not repeat itself above figure have 3.5 cycles part above from zero line called +ve cycle and half-cycle is called alternation.


The time required to complete one cycle is called period an ac current cover one cycle in about 0.25 s.


The number of cycles per second called 1 frequency and it is equal to reciprocal of time. The unit of

f = 1 / t

frequency is hertz (Hz).

Specifying Amplitude:

We can specify amplitude in different ways and these things are very important for basics.

Peak Value: 

The value from reference point to max point is called peak value it can be +ve or -ve.

Peak-to-Peak Value:

The value from max +ve point to max -ve point is called peak-to-peak value or it is twice of peak value                                                                      Vp-p=2 Vp

Average Voltage:

is 0.637 times of peak voltage           Vav = 0.637 Vp

The most important way of specifying the amount of alternating current by stating it’s effective or rms value. The effective is the value that produces the same heat in a resistive circuit as a direct current of the same value.

The Sine Wave:

There are following things which define sine wave.

Induced Voltage and Current:

When a conductor cuts across magnetic flux it produces voltage this voltage cause current to flow if there is complete circuit. The induced voltage is amount of flux cut by conductor per unit time and it is determined by following

1. The speed of conductor

2. The flux density

3. The angle at which the conductor crosses the magnetic flux

Producing Sine Wave:

1. When conductor is parallel to magnetic flux then no voltage induce.

2. When conductor starts moving small amount of voltage induces because few flux lines are passing through conductor so sine wive start forming.

3. When conductor is perpendicular to flux then sine wave got its peak value and flux is maximum.

4. Then again flux starts decreasing and now it’s amplitude is negative and we know that no current is induced when polarity is negative hence one cycle complete.

To determine direction of induced current we use Fleming’s Left Hand Rule


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-Power in AC Circuits