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प्रश्न
A pivoted aluminium bar falls much more slowly through a small region containing a magnetic field than a similar bar of an insulating material. Explain.
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उत्तर
An aluminium bar falls slowly through a small region containing a magnetic field because of the induced eddy currents (or induced emf) in it. According to Lenz's law this induced eddy current oppose its cause (its motion). Hence, it slows down while falling through a region containing a magnetic field. On the other hand, non-metallic or insulating materials are free from such effects.
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संबंधित प्रश्न
Describe a simple experiment (or activity) to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it.
Predict the direction of induced current in the situation described by the following figure.
Use Lenz’s law to determine the direction of induced current in the situation described by the figure:
A wire of irregular shape turning into a circular shape.
Show that Lenz's law is a consequence of conservation of energy.
Predict the direction of induced current in a metal ring when the ring is moved towards a straight conductor with constant speed v. The conductor is carrying current I in the direction shown in the figure.
A bar magnet is moved in the direction indicated by the arrow between two coils PQ and CD. Predict the directions of induced current in each coil.
Consider the situation shown in figure. If the switch is closed and after some time it is opened again, the closed loop will show ____________ .
Lenz’s law is a consequence of the law of conservation of ______.
2 A 40 kg boy whose legs are 4 cm in area and 50 cm long falls through a height of 2 m without breaking his leg bones. If the bones can withstand stress of 0.9 x 108 N/m2. The Young's modulus for the material of the bone is ______.
Young's modulus for aluminium is 7 × 1010 Pa. The force needed to stretch an aluminium wire of diameter 2 mm and length 800 mm by 1 mm is ______.
Energy dissipate in LCR circuit in
Lenz's law gives ______
Same as problem 4 except the coil A is made to rotate about a vertical axis (figure). No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this instant, t = 0, is ______.
A conducting wire XY of mass m and neglibile resistance slides smoothly on two parallel conducting wires as shown in figure. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a ˆ. magnetic field `B = B(t)hatk`.
- Write down equation for the acceleration of the wire XY.
- If B is independent of time, obtain v(t) , assuming v(0) = u0.
- For (b), show that the decrease in kinetic energy of XY equals the heat lost in R.
A metallic ring of mass m and radius `l` (ring being horizontal) is falling under gravity in a region having a magnetic field. If z is the vertical direction, the z-component of magnetic field is Bz = Bo (1 + λz). If R is the resistance of the ring and if the ring falls with a velocity v, find the energy lost in the resistance. If the ring has reached a constant velocity, use the conservation of energy to determine v in terms of m, B, λ and acceleration due to gravity g.
A long solenoid ‘S’ has ‘n’ turns per meter, with diameter ‘a’. At the centre of this coil we place a smaller coil of ‘N’ turns and diameter ‘b’ (where b < a). If the current in the solenoid increases linearly, with time, what is the induced emf appearing in the smaller coil. Plot graph showing nature of variation in emf, if current varies as a function of mt2 + C.
Predict the direction of induced current in the situation described by the following figure.
Predict the direction of induced current in the situation described by the following figure.
