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Explain why the direction of the induced current in the coil of an AC generator changes after every half revolution of the coil.
Fig. : AC generator
The axle of an AC generator is rotated such that one arm AB moves up and other CD moves down. The change in the magnetic field linked to the coil induces current in the coil. From Fleming’s right hand rule, the current flows from AB to CD in the coil during half rotation and from B2 to B1 in the external circuit.
After half rotation, the arm CD starts moving upward and AB downwards. So, the current starts flowing from CD to AB by Fleming’s Right hand rule. As a result the current starts flowing from B1 to B2 in the external circuit after half rotation.
In this way, the direction of induced current changes after each half rotation in an AC generator.
Fig. : Fleming’s right hand rule.
A student while studying the force experienced by a current-carrying conductor kept in a magnetic field records the following observations:
i. The force experienced by the conductor increases as the current is increased.
ii. The force experienced by the conductor decreases as the strength of the magnetic field is increased.
Which of the two observations is correct and why?
Two coils 1 and 2 of insulated copper wire having large but different number of turns are wound over a cardboard cylinder. Coil 1 is connected to battery and a plug key. Coil 2 is connected to a galvanometer.
How will the galvanometer reading change when
(i) key is plugged in and
(ii) key is taken out? Give reason for your answer in each case.
A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the board gently and observes that the iron filings arrange themselves in a particular pattern.
a. Why do the iron filings arrange in a pattern?
b. What does the crowding of iron filings at the end of the magnet indicate?
c. What does the lines along which the iron filings align represent?
d. Draw a neat diagram to show the magnetic field lines around a bar magnet.
e. Write any two properties of magnetic field lines.
a. A stationary charge is place in a magnetic field. Will it experience a force? Give reason to justify your answer.
b. On what factors does the direction of force experienced by a conductor when placed in a magnetic field depend?
c. Under what conditions is the force experienced by a current carrying conductor placed in a uniform magnetic field maximum?
d. under what conditions is the force experienced by a current carrying conductor placed in a uniform magnetic field maximum?
Two coils C1 and C2 are wrapped around a non conducting cylinder. Coil C1 is connected to a battery and key and C2 with galvanometer G. On pressing the key (K), current starts flowing in the coil C1. State your observation in the galvanometer:
i. When key K is pressed on.
ii. When current in the coil C1 is switched off.
iii. When the current is passed continuously through coil C.
iv. Name and state the phenomenon responsible for the above observation. Write the name of the rule that is used to determine the direction of current produced in the phenomena.