Tag: effects of electric current

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Questions Related to effects of electric current

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

Principle behind electric generator is

  1. when a straight conductor is moved in the electric field, then current is induced in the conductor.

  2. when a circular loop is moved in electric field, then current is induced in the conductor.

  3. when a straight conductor is moved in a magnetic field, the current is induced in the conductor.

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electric generator is the application of EMI. The electric generator woeles on the principle that when a straight conductor is moved in magnetic field, then current is induced in the conductor.

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

When the plane of the rectangular coil is parallel to the direction of the magnetic field in a dynamo, then

  1. Induced current will be zero.

  2. Induced current is maximum.

  3. AC is produced.

  4. DC is produced.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When the plane of the rectangular coil is parallel to the magnetic field, angle between the magnetic field and the area vector of coil  $\theta = 90^o$
Flux passing though the coil  $\phi = BA \ \cos\theta = BA \ \cos90^o = 0$
Thus no emf is induced in the coil and induced current is zero.

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

Which instrument works on the principle of "Electromagnetic induction?

  1. Electric motor

  2. Fuse

  3. Electric bell

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

An electric generator converts mechanical energy into electrical energy based on Faraday's law of electromagnetic induction. An electric motor works on the force exerted on a current-carrying conductor in a magnetic field, while a fuse and bell operate on thermal and magnetic effects respectively.

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

In an a.c. generator the speed at which the coil rotates is doubled. How would this affect the frequency of output voltage ?

  1. Frequency of maximum output voltage is halved.

  2. Frequency of maximum output voltage is doubled.

  3. Frequency of maximum output voltage remains same.

  4. Insufficient data.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
In an a.c. generator, emf produced is,

    $e=NAB(2\pi v)sin(2\pi v)t$

          where $N=$ no. of turns

                      $A=$ cross- sectional area

                      $B=$ magnetic field.

A frequency of ac, $v=\dfrac{w}{2\pi}$

                    where $w=$ is the speed of rotation

From the above, Frequency of maximum output voltage is directly proportional to speed of rotation of coil.

B. Frequency of maximum output voltage is double.
Multiple choice physics effects of electric current electric generator ac generator magnetic effects of electric current

In an AC generator, maximum number of lines of force pass though the coil when the angle between the plane of coil and lines of force is :

  1. $0^{\circ}$
  2. $60^{\circ}$
  3. $30^{\circ}$
  4. $90^{\circ}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is D.

The emf is actually induced by a change in the quantity called the magnetic flux rather than simply by a change in the magnetic field. Magnetic flux is proportional to both the strength of the magnetic field passing through the plane of a loop of wire and the area of the loop. The value of the magnetic flux is proportional to the total number of lines passing through the loop. When the area is perpendicular, that is, at right angles (90 degrees) to the lines, the maximum number of lines passes through the area and the flux is a maximum. When the area is parallel to the lines, no lines pass through the area and the flux is 0.
Hence, maximum number of lines of force passes though the coil when the angle between the plane of coil and lines of force is 90 degrees.

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

What energy conversion takes place in a generator ?

  1. mechanical energy into magnetic energy.

  2. mechanical energy into chemical energy.

  3. mechanical energy into electric energy.

  4. electrical energy into mechanical energy.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Answer is C.

The generation of electrical power requires relative motion between a magnetic field and a conductor. In a generator, mechanical energy is converted into electrical energy. The electricity produced by most generators is in the form of alternating current. In general, AC generators, motors and other electrical equipment are simpler, cheaper and more reliable than their DC counterparts.  AC electricity can be easily transformed into higher or lower voltages making it more versatile than DC electricity.