In items 11 through 30, select the best answer to make each...

In items 11 through 30, select the best answer to make each statement true. Place the letter of your answer in the space provided. The alternating EMF generated in the single-loop armature of a two-pole generator reverses once every____ a. revolution. c. quarter-revolution. b. half-revolution. d. two revolutions.

In items 11 through 30, select the best answer to make each statement true. Place the letter of your answer in the space provided.
The alternating EMF generated in the single-loop armature of a two-pole generator reverses once every____
a. revolution.
c. quarter-revolution.
b. half-revolution.
d. two revolutions.

Key Concepts

Electromagnetic Induction

This concept involves the generation of an electromotive force (EMF) in a conductor by changing the magnetic flux through it, as stated by Faraday’s Law of Induction. It is the fundamental principle behind most electrical generators, where a rotating coil in a magnetic field experiences a changing flux that induces an alternating voltage.

Operation of AC Generators

In AC generators, the design of the armature and magnetic field arrangement ensures that the induced voltage changes polarity periodically. Specifically, in a single-loop armature within a two-pole generator, the polarity of the induced EMF reverses when the loop rotates through half of a complete revolution, creating the alternating current characteristic.

Transcript

00:01 Hi, in the given problem here this is the graph between the emf induced in the generator coil with respect to time.

00:29 So this is the curve over which the time has been mentioned to be 0 .03 here and 0 .06 here.

00:51 This time is measured in seconds.

00:56 And here this is the emf induced over the y -axis.

01:03 Area of the coil of the generator is given as a is equal to 0 .15 meter square.

01:16 Number of turns in this coil is 10 and the magnetic field is 0 .27 tesla in which this coil is rotating.

01:28 So first of all, we have to discuss few concepts.

01:33 The first concept, ask, can the period of rotating go be determined from the graph? the answer is yes, because one crest and one trough together, taken together gives one time period as one rest and one drop taken together gives one time period.

02:15 With the help of given graph, we can find the time period.

02:38 You can find the period of rotating coil or the period of emf induced.

02:50 Both of them will be same.

02:53 Now, in the second concept, they're asking the emf produced by the generator depends on its angular frequency.

03:02 How is the angular frequency of the coil related to the time period? so angular frequency means angular velocity also, which is given as the ratio of the angle means angular displacement made by the coil per unit.

03:26 So we know if that in a complete rotation the angle made by this coil will be 2 pi and in that rotation the time taken in that rotation will be termed as time period so capital t.

03:44 So angular frequency is given as 2 pi by t.

03:50 The second concept.

03:54 In the third concept starting from 0 second, how much time is required for the generation? to produce its peak emf.

04:05 So looking at this curve, starting from the time equals to 0, this is the first peak emf here.

04:15 This time is the total time period.

04:19 So up to here it will be t by 2.

04:22 So up to here it will be t by 4.

04:26 So in the third concept, starting from t equals to 0, how much time is required and you have to express the answer in terms of time period.

04:41 So that time is clearly one -fourth of the total time period.

04:47 Or we can say this is 0 .25 of the total time period capital t.

04:55 Now in the fourth concept, how often does the polarity of the emf change in one cycle? so it is clear that the polarity of the emf is changing twice in a complete cycle of rotation...

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