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प्रश्न
State the working of a.c. generator with the help of a labeled diagram.
The coil of an a.c. generator having N turns, each of area A, is rotated with a constant angular velocity ω. Deduce the expression for the alternating e.m.f. generated in the coil.
What is the source of energy generation in this device?
उत्तर
AC Generator:
Principle − Based on the phenomenon of electromagnetic induction
Construction:
Main parts of an ac generator:
• Armature − Rectangular coil ABCD
• Filed Magnets − Two pole pieces of a strong electromagnet
• Slip Rings − The ends of coil ABCD are connected to two hollow metallic rings R1 and R2.
• Brushes − B1 and B2 are two flexible metal plates or carbon rods. They are fixed and are kept in tight contact with R1 and R2 respectively.
Theory and Working − As the armature coil is rotated in the magnetic field, angle θ between the field and normal to the coil changes continuously. Therefore, magnetic flux linked with the coil changes. An emf is induced in the coil. According to Fleming’s right hand rule, current induced in AB is from A to B and it is from C to D in CD. In the external circuit, current flows from B2 to B1.
To calculate the magnitude of emf induced:
Suppose
A → Area of each turn of the coil
N → Number of turns in the coil
`vecB`→ Strength of magnetic field
θ → Angle which normal to the coil makes with at any instant t
∴ Magnetic flux linked with the coil in this position:
`phi = N(vecB *vecA)`= NBA cos θ = NBA cos ωt …(i)
Where, ‘ω’ is angular velocity of the coil
As the coil rotates, angle θ changes. Therefore, magnetic flux Φ linked with the coil changes and hence, an emf is induced in the coil. At this instant t, if e is the emf induced in the coil, then
`e =-(d theta)/dt = -d/dt(NAB cos omegat)`
` =-NAB d/dt (cos omegat)`
`=-NAB (-sin omegat)omega`
∴e = NAB ω sin ωt
The generator converts the mechanical energy into electrical energy. The mechanical energy may be obtained from the rotation of the turbine associated with the generator. The turbine in turn, may be working by the kinetic energy of running water, wind or steam.
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संबंधित प्रश्न
State the principle on which the AC generator works. Draw a labelled diagram and explain its working.
State A.C. generator underlying principle?
Answer in brief.
For a very high-frequency AC supply, a capacitor behaves like a pure conductor. Why?
When the plane of the armature of a generator is parallel to the field. in which it is rotating ______.
A resistor, capacitor, and inductor are connected in series across an AC generator. Which of the following statements is false?
A common transistor radio set requires 12 V (D.C.) for its operation. The D.C. source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V (A.C.) on standard domestic A.C. supply. The number of turns of secondary coil are 24, then the number of turns of primary are ______.
Briefly describe the working of ac generator.
Obtain the expression for the instantaneous value of emf induced.
With the help of a labelled diagram, describe the principle and working of an ac generator. Hence, obtain an expression for the instantaneous value of the emf generated.
An AC generator spinning at a rate of 750 rev/min produces a maximum emf of 45 V. At what angular speed does this generator produce a maximum emf of 120 V?
