## EMF induced in single phase system

We know that an **alternating emf** can be generated either by rotating a coil within a stationary magnetic field, as illustrated in fig.(a) or by rotating a magnetic field within a stationary coil, as illustrated in fig.(b). The emf generated, in either case, will be of sinusoidal waveform. The magnitude of **emf** generated in the coil depends upon the number of turns on the coil, the strength of **magnetic field** and the speed at which the coil or magnetic field rotates. The former method is employed in case of small ( **single phase generation **) **ac generators** while the later one is employed for large sized **ac generators**.

Now, consider a rectangular coil of N turns rotating in counter-clockwise direction with angular velocity of radians per second in a **uniform magnetic field**, as illustrated in fig. (c).

Let, the time be measured from the instant of coincidence of the plane of the coil with the X-axis. At this instant **maximum flux**,

links with the coil. Let the coil assume the position, as shown in figure, after moving in counter-clockwise direction for t seconds.

In this position, the component of flux perpendicular to the plane of coil =

Hence, flux linkages of the coil at this instant — Number of turns on coil x linking flux

i.e. instantaneous flux linkages

Since, emf induced in a coil is equal to the rate of change of flux linkages with minus sign. **EMF induced** at any instant,

So, the **emf induced** varies as the sine function of the time angle wt, and if **emf induced** is plotted against time, a curve of sine wave shape is obtained as illustrated in figure (d). Such an emf is called the sinusoidal emf The sine curve is completed when the coil rotates through an angle of 2 pie radians. The induced **emf** e will have maximum value, represented by Emax , when the coil has turned through pie/2 radians (or 90^{0} ) in counter- clockwise direction from the reference axis (i.e. 0X axis).

## A.C. CIRCUITS TOPIC

- Introduction Of AC Circuits In Electrical Engineering
- How emf is induced in single phase system ? single phase generation .
- Explain what is ac quantity : and Advantages of AC over DC in circuits
- What is waveform, amplitude, cycle, time-period, phase & phase difference
- Define RMS & average value as applied to A.C. voltage & current
- What is form factor? crest factor? peak factor? & power factor? in ac circuits
- what is phasor diagram, phasor algebra, leading & lagging ac quantities
- Phasor representation of alternating quantities – resistive, inductive, capacitive
- What is R-L-C series connection for A.C. circuit ? Explanation
- What is series combination of R-L circuit ? Explanation
- Define what is active power, reactive power, apparent power & power factor
- Explain what is series combination of R-C circuit in electrical engineering
- What is simple parallel AC circuits ? Explanation -electrical engineering
- Resonance as applicable to simple RLC series circuit? effect on circuit performance
- Explain three phase generation of voltage ? electrical engineering
- Explain in detail about what is star and delta three phase system ?
- Relation between phase voltage & line voltage in case of balanced star connected load
- relationship between line current & phase current for delta connected 3 load
- Relation between power consumed in a balanced star & delta connection

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