Question Pool Electromagnetic Induction

Electromagnetic Induction - SAMAGRA Question Pool & Answers | Class 10 English Medium

Kerala Syllabus SAMAGRA SCERT SAMAGRA Question Pool for Class 10 English Medium Physics Electromagnetic Induction

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Qn 1.

The figure of a generator is given below

  1. What do the parts X , A represent in the figure.
  2. What is the energy change occurs in such a device.
  3. What is the use of part Y in the figure
  • Answer)
    1. X-slip ring, A-armature
    2. Mechanical energy changes to electrical energy.
    3. supply electrical energy to external circuit
Qn 2.

The figure shows a resister, galvanometer connected to a 6V battery.

  1. In what way the instruments got connected in the circuit.
  2. In which direction does the galvanometer needle deflects.
  3. If the battery is replaced by an AC source, what change may be observed in the deflection of galvanometer needle? Why?
  • Answer)
    1. series combination
    2. single direction only
    3. direction reverses continuously
Qn 3.

In our country the frequency of AC produced for transmission is 50Hz.

  1. What does it mean by frequency of an AC?
  2. In one second, how many times the direction of EMF change?
  • Answer)
    1. number of cycles in one second
    2. 50 times
Qn 4.

Observe the figures a,b,c given below and answer the questions (Solenoid,Bar magnet and galvanometer)

  1. In which solenoid the intensity of current is more?
  2. What will be the change in deflection of the galvanometer if the magnet in b &c circuits get into the solenoid.
  • Answer)
    1. a
    2. galvanometer needle in circuit b deflects in opposite direction to the deflection of galvanometer needle in circuit c.
Qn 5.

An armature coil of an AC generator when moved in the magnetic field, induced current is produced.

  1. Which is the law that helps to find the direction of current.
  2. As per the law what does the fore finger represent?
  • Answer)
    1. Flemings right hand rule
    2. Magnetic field
Qn 6.

Whenever change occurs to the magnetic flux connected to a closed circuit, a current is induced.

  1. What is this phenomenon known as?
  2. Name an instrument that works based on this principle.
  • Answer)
    1. Electromagnetic Induction
    2. Microphone/generator
Qn 7.

Find out the correct statement/statements from those given below.

  1. when a magnet is moved close to a solenoid, the magnetic flux linked with the solenoid will decrease.
  2. when a magnet is moved close to a solenoid, the magnetic linked with the solenoid will increase.
  3. when a magnet is moved close to a solenoid, the magnetic flux linked with the solenoid remains the same
  • Answer)

    b. when a magnet is moved close to a solenoid, the magnetic linked with the solenoid will increase

Qn 8.

The figure given below shows an instrument that changes sound energy into electrical energy.

  1. Name the parts A and B in the figure?
  2. In such an instrument, explain how the sound energy is changed into electrical energy?
  • Answer)
    1. A-Diphrgam, B-Voice coil
    2. When sound signal falls on diaphrgam it vibrates.This causes voices coil to vibrate placed in magnetic field. Flux linked with the voice coil changes and electrical signals are produced 
Qn 9.

Some relations regarding transformers are given below. Among these select and write down the one that relates to step up transformers.

  1. Vs> Vp
  2. Is < Ip
  3.  Is > Ip
  4. Vp>Vs
  • Answer)
    1. Vs> Vp
    2.  Is < Ip
Qn 10.

Correct error in the underlined part of the following statements if any

  1. To complete one cycle of an AC, an armature needed to rotate 3600.
  2. if frequency of an AC is 50Hz, the armature completes 25 cycles per second.
  3. In an AC generator, current reverses direction in each half rotation
  • Answer)

    a. AC of frequency is 50Hz has 50 cycles per second.

    b. In an AC generator, electric current flows in one direction for the first half rotation and reverses direction in the next half.

Qn 11.

 A transformer has 10000 turns and 240V , 0.2A in the primary coil. If the current through secondary coil is 0.4A.

  1. What kind of transformer is this?
  2. Find out the voltage and number of turns in the secondary coil.
  3. Calculate maximum power in the secondary coil of this transformer.
  • Answer)
    1. Step-Down Transformer
    2. Vp x Ip = Vs x Is                                                                                                          Vs = 240 x 0.2 / 0.4 = 120 V                                                                                    Vs/Vp = Ns/Np                                                                                                          120/240 = Ns/ 10000                                                                                                 Ns = 120 x 10000 / 240 = 50000 nos
    3. P = VI = 240 x 0.2 = 48 W 
Qn 12.

Given below is the figure of a transformer

  1. What kind of transformer is shown here?
  2. why thick coil is used in the secondary of the transformer.

 

  • Answer)
    1. step-down transformer
    2. secondary current increase

     

Qn 13.

The figures of the two stages of an armature that rotates in a magnetic field is shown below.

  1. Select the figure in which plane of the armature coil comes parallel to the magnetic field.
  2. identify the stage where emf induced is maximum.
  3. Compare the stages (i), (ii) and explain change in the magnitude of emf.

 

  • Answer)
    1. fig b
    2. fig b
    3. stage1- No flux variation and emf=0                                                                      stage 2- Flux variation is maximum.so, emf is maximum

     

Qn 14.

Name the electronic components given below.

  1.  If each of these is connected to an AC circuit, which circuit has more power loss?Why?

 

  • Answer)
    1. Resistor
    2. Inductor
    1. circuit containing resistor. A resistor causes wastage of energy in the form of heat

     

Qn 15.

Given below is the picture of a transformer.

  1. If 12V DC is given as input, how much is the output voltage.
  2. If 12V AC is given as the input, what would be the out put voltage.
  3. At this juncture what is the voltage in one coil of the secondary.

 

  • Answer)
    1. 0 V                                                                         
    2. Vs/Vp = Ns/Np                                                                                                              Vs = (Ns/Np ) x Vp                                                                                                             = (2000/100 ) * 12 = 240 V         
    3. Vs = Ns x e                                                                                                                      e = Vs/Ns ,=240/2000 = 0.12 V      
Qn 16.

Find out the odd one and Justify your answer.                                                                Microphone, loud speaker, Transformer, Generator

  • Answer)

    Loud speaker.                                                                                                                      All other devices works based on electromagnetic induction

Qn 17.

By increasing diameter of conductors, transmission loss could be reduced.

  1. What are the difficulties that arises if thick wires used as transmission lines.
  2. Suggest another method to reduce transmission loss.
  • Answer)
    1. if thickness increases , weight increases, more supporting beams are required and expense increases
    2. decrease current by increasing voltage
Qn 18.

Identify the relation in the first pair and complete the following:                                   Electro-magnetic induction: Moving coil microphone                                                   Mutual Induction :..............................

  • Answer)

    Transformer

Qn 19.

The number of turns in the primary of a transformer is two times greater than that in the secondary, then

  1. identify the type of transformer?
  2. If 50V is given to the primary, What will be the voltage obtained in the secondary?
  3. If the current in its primary coil is 4A What will be the current in the secondary?
  • Answer)
    1. step up transformer
    2. 50 x 2 = 100 V
    3. Vp x Ip = Vs x Is                                                                                                               50 x 4 = 100 x Is                                                                                                          Is = 200 /100 = 2 A 
Qn 20.

Find out the relation and fill in the blanks

Generator:

Armature

Induced emf

Moving coil microphone

......................

Induced emf
  • Answer)

    Voice Coil

Qn 21.

Select and write down the correct statements regarding a step down transformer from those given below.

  1. current is same in primary and secondary.
  2. Power is same in primary and secondary.
  3. as compared to the secondary coil current Primary coil current is less.
  4. Current in the secondary is less than the current in the primary.
  • Answer)

    b. Power is same in primary and secondary.                                                                        c. Primary current is less than secondary current.

Qn 22.

  1. which instrument is shown above? What is its working principle?
  2. When 100V AC is applied at A ,the current was 2A. Calculate the Voltage and current received at B.
  • Answer)
    1. transformer, mutual induction
    2. Vs/Vp = Ns/Np= Vs/100 = 5000/10000                                                                               Vs = 50 V                                                                                                            P= V I = 100 x 2 = 200 W , input power=output power
Qn 23.

The figure shows copper coils of same thickness and different turns arranged in four circuits. If all the bulbs are of same power answer the following questions analysing each figure.

  1. If all the circuits are kept on ,which bulb in the circuit glows with least intensity. Justify your answer.
  2. If a soft iron core of the same size is inserted in each of the coils, which among the circuits shows most change in the intensity of light..
  • Answer)
    1. circuit 4                                                                                                                    Self induction is more if number of turns is more. So back emf increases.
    2. circuit 4 , if iron core is inserted self induction again increases
Qn 24.

Identify the relationship between the terms in the first pair and fill up the second pair accordingly:                                                                                                                Generator  :  Armature                                                                                                  Moving coil microphone   :    ..............

  • Answer)

    voice coil

Qn 25.

The figure of a DC generator is given below.

  1. What is the structural deference of DC generator and AC generator.
  2. Compare the energy change taking place in an electric motor and a DC generator.
  3. Through the current produced in a DC generator is AC, DC is received in the output. How?

 

 

  • Answer)
    1. Slip rings used in Ac generator and Split rings used in DC generator.
    2. Motor: Electrical energy changes to mechanical energy.                                          DC generator: Mechanical energy changes to electrical energy
    3. The direction of elecTric current changes in each half rotation.The brushes connected to external circuit always comes in contact with armature which moves in the same direction. So direction of external current does not change 
Qn 26.

Identify the relation in the first pair and complete the second pair.

Generator

Mechanical energy is changed in to electrical energy

Moving coil microphone

........................................................

 

  • Answer)

    sound energy changes to electrical energy

Qn 27.

The current in the primary of a step up transformer that has no energy loss is........            (More, Less, equal)

  • Answer)

    More

Qn 28.

First part of a house hold circuit is shown in the figure:

  1. Draw the diagram as it is, and label all instruments.
  2. Complete the circuits after drawing with the inclusion of two lambs , one fan, one three pin plug for a newly build room.
  3. Draw the circuit diagram which includes two lambs , one fan and a three pin plug
  • Answer)
    1. Main fuse, Main Switch, MCB, ELCB, watt-hourmeter
    2. copy the figure and introduce instruments
Qn 29.

Observe the figure and answer the questions given.

  1. If 6V AC is used instead of DC in this circuit then brightness of the bulb decreases. Name the phenomenon that causes this decrease of brightness ?
  2. What change may occur if a soft iron core is inserted to the coil?

 

  • Answer)

    Self Induction

    Self induction is a phenomenon by which a changing electric current produces an induced emf across the coil itself.


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