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प्रश्न
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflection depends. State the laws describing this phenomenon.
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उत्तर
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects because of the phenomenon of electromagnetic induction.
Factors on which the amount and direction of deflection depend are
(i) Speed of the magnet
(ii) Polarity of the magnet
Laws describing electromagnetic induction are
(1) Faraday’s law of electromagnetic induction: The magnitude of the induced emf in a circuit is equal to the time rate of change of magnetic flux through the circuit.
`epsilon=-(dphi)/dt`
(2) Lenz’s law: The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it.
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संबंधित प्रश्न
A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s−1 in a direction normal to the
- longer side,
- shorter side of the loop?
For how long does the induced voltage last in each case?
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When current is 'switched on' and 'switched off' in a coil, a current is induced in another coil kept near it. What is this phenomenon known as?
Describe one experiment to demonstrate the phenomenon of electromagnetic induction.
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(b) `R/L`
(c) `1/sqrt(LC)`
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What is an electromagnet?
State the purpose of soft iron core used in making an electromagnet.
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards end B of the coil, a deflection is observed in the galvanometer.
- State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
- What would be observed in the galvanometer in a situation when the coil and the bar magnet both move with the same speed in the same direction? Justify your answer.
- State the conclusion that can be drawn from this activity.
Will there be any change in the momentary deflection in the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil?
OR
What is electromagnetic induction? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns? Justify your answer.
