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Multiple choice physics magnetic effects of electric current electric generator ac generator effects of electric current

Suggest way/s in an a.c. generator to produce a higher e.m.f.

  1. By increasing the speed of rotation of coil

  2. By increasing the number of turns in the coil

  3. both A & B

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
C. both A & B.
In an a.c. generator to produce a higher emf-
1. By increasing the speed of rotation of the coil.
2. By increasing the number of turns in the coil.
Multiple choice physics magnetic effects of electric current electric generator ac generator effects of electric current

The laws of electromagnetic induction have been used in the construction of a :

  1. galvanometer

  2. voltmeter

  3. electric motor

  4. electric generator
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The laws of electromagnetic induction has been used in the construction of a electric generator. In electric generator, emf is induced by changing the flux.
Galvanometer is used to detect current. So, no use of electromagnetic induction.
Voltmeter is used to measure voltage. Again, no use of electromagnetic induction.
Electric motor changes electrical energy into mechanical energy, which has no use of laws of electromagnetic induction.

Multiple choice physics magnetic effects of electric current electric generator ac generator effects of electric current

A D.C. generator is based on the principle of.

  1. magnetic effect ofcurrent

  2. lighting effect ofcurrent

  3. electrochemical induction

  4. electromagnetic induction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is D.

Electromagnetic induction is a process where a conductor placed in a changing magnetic field (or a conductor moving through a stationary magnetic field) causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current - it is said to induce the current.
Hence, the D.C. generator is based on the principle of electromagnetic induction.

Multiple choice physics effects of electric current electric generator ac generator magnetic effects of electric current

In an electric generator ,split rings are used for 

  1. Converting DC to AC

  2. Converting AC to DC

  3. Reducing power consumption

  4. To split the current
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

The electric generator is devised to convert mechanical power into electrical power. Permanent magnet (PM) current converts into electrical energy through the interaction of two magnetic fields. One field is produced by a permanent magnet assembly, the other field is produced by an electrical current flowing in the rectangular coil ABCD, through the brushes and split-ring commutators. These two fields result in a torque which tends to rotate the coil. As the coil turns, the current in the winding is commutated to produce a continuous torque output. 
The split ring commutator is made from 2 pieces of copper that are held apart in the center from touching each other. They look like a copper ring split in the middle. The effect of using split rings in a electric generator is that the direction of the current flowing in the coil is reversed and DC current is generated.

Multiple choice physics effects of electric current electric generator ac generator magnetic effects of electric current

If the speed of rotation of armature coil is increased in an AC generator

  1. Magnitude of current increases

  2. Frequency of current increases

  3. Both 1 and 2

  4. Magnitude of current increases, frequency decreases
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If the speed of rotation of armature coil is increased in an AC generator

$\mathscr{E} = NAB\omega  \sin \theta$,Magnitude of current increases,Frequency of current increases The option C is correct.

Multiple choice physics effects of electric current electric generator ac generator magnetic effects of electric current

A feature common to both AC and DC generator is ______.

  1. Split rings

  2. Electrical energy is converted to mechanical energy

  3. Slip rings

  4. Mechanical energy is converted to electrical energy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Electric generator, also called dynamo, any machine that converts mechanical energy to electricity for transmission and distribution over power lines to domestic, commercial, and industrial customers. Generators also produce the electrical power required for automobiles, aircraft, ships, and trains.A feature common to both AC and DC generator is Mechanical energy is converted to electrical energy

Multiple choice physics effects of electric current electric generator ac generator magnetic effects of electric current

In an AC generator, the rate of change of magnetic flux through the coil is maximum when the angle between the plane of the coil and the lines of force is

  1. $0^0$

  2. $60^0$

  3. $30^0$

  4. $90^0$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an AC generator,  Magnetic flux $= NAB\sin\phi$

And, the rate of change of magnetic flux through the coil $(\dfrac{\mathrm{d}\phi }{\mathrm{d} t})$ $= NAB\omega\cos\phi$
So, the rate of change of magnetic flux through the coil is maximum when  $NAB\omega\cos\phi$ is maximum
$\Rightarrow \cos\phi$ is maximum
$\Rightarrow \cos\phi = 1$
$\Rightarrow \phi = 0^0$
Therefore, A is correct option.