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Question : 14
Total: 15
(a) State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
(b) 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.
(c) State the conclusion that can be drawn from this activity.
Will there by any change in the momentary deflection in the galvanometer if number of turns in the coil 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.
Solution:
(a) A galvanometer is an instrument that can detect the presence of a current in a circuit. The pointer remains at zero (the centre of the scale) for zero current flowing through it. Pointer can deflect either to the left or to the right of the zero-mark depending on the direction of current. There is a momentary deflection in the needle of the galvanometer to the right. This indicates the presence of a current in the coil AB
(b) When the coil and bar magnet both move with the same speed in the same direction then there is no change in the magnetic field across the cell hence no induced current. This is as per Michael Faraday's law of electromagnetic induction which states: "that a voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux".
(c) From this activity it can be concluded that motion of a magnet with respect to the coil produces an induced potential difference, which sets up an induced electric current in the circuit.
1. Increasing the number of turns of wire in the coil. - By increasing the number of individual conductors cutting through the magnetic field, the amount of induced emf produced will be the sum of all the individual loops of the coil.
2. Increasing the strength of the magnetic field. - If the same coil of wire is moved at the same speed through a stronger magnetic field, there will be more emf produced because there are more lines of force to cut.
OR
Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field. It 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.
Electromagnetic Induction was discovered by Michal Faraday in 1831. Either the conductor is placed in a moving magnetic field or a moving conductor is placed in a stationary magnetic field. The production of electricity form magnetism is called electromagnetic induction. A galvanometer is an instrument that can detect the presence of a current in a circuit. A current is induced in a coil when it is moved (or rotated) relative to a fixed magnet. A current is also induced in a fixed coil when a magnet is moved (or rotated) relative to the fixed coil. When the coil and bar magnet both are held stationary relative to one another then there is no change in the magnetic field across the cell hence no induced current. When the direction of motion of coil (or magnet) is reversed, the direction of current induced in the coil also gets reversed.
(b) When the coil and bar magnet both move with the same speed in the same direction then there is no change in the magnetic field across the cell hence no induced current. This is as per Michael Faraday's law of electromagnetic induction which states: "that a voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux".
(c) From this activity it can be concluded that motion of a magnet with respect to the coil produces an induced potential difference, which sets up an induced electric current in the circuit.
1. Increasing the number of turns of wire in the coil. - By increasing the number of individual conductors cutting through the magnetic field, the amount of induced emf produced will be the sum of all the individual loops of the coil.
2. Increasing the strength of the magnetic field. - If the same coil of wire is moved at the same speed through a stronger magnetic field, there will be more emf produced because there are more lines of force to cut.
OR
Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field. It 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.
Electromagnetic Induction was discovered by Michal Faraday in 1831. Either the conductor is placed in a moving magnetic field or a moving conductor is placed in a stationary magnetic field. The production of electricity form magnetism is called electromagnetic induction. A galvanometer is an instrument that can detect the presence of a current in a circuit. A current is induced in a coil when it is moved (or rotated) relative to a fixed magnet. A current is also induced in a fixed coil when a magnet is moved (or rotated) relative to the fixed coil. When the coil and bar magnet both are held stationary relative to one another then there is no change in the magnetic field across the cell hence no induced current. When the direction of motion of coil (or magnet) is reversed, the direction of current induced in the coil also gets reversed.
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