Class 12th Physics 2017 Set3 Delhi Board Paper Solution
Distinguish between unpolarised light and linearly polarised light. How does one get linearly polarised light with the help of a polaroid?
Unpolarised light: A light wave in which electric vector oscillates in all possible directions in a plane perpandicular to the direction of propagation is called unpolarised light as shown in the below image:
Linearly polarised: if the electric vector's vibration is restricted to one direction only in a plane perpandicular to the direction of propagation. the light is called linearly polarised.
As shown in the below image:
Polaroid is a special crystalline solid which contains a special axis called optic axis. When we make a unpolarised light to fall on a polaroid, only vibration parallel to optic axis is allowed to pass through and all other vibration are cut. Thus, the output is a plane polarised light.As shown in the below image:
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A 600 pF capacitor is charged by a 200 V supply. It is then disconnected from the supply and is connected to another uncharged 600 pF capacitor. How much electrostatic energy is lost in the process?
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A regular hexagon of side 10 cm has a charge 5 µC at each of its vertices. Calculate the potential at the centre of the hexagon.
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A point charge +10 μC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)
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A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 103 N/C and points radially inward, what is the net charge on the sphere?
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A point charge of 2.0 μC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
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Two charges 5 x 10-8 C and -3 x 10-8 C are located 16 cm apart. At what point(s) on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.
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Answer the following questions:
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A toroid has a core (non-ferromagnetic) of inner radius 25 cm and outer radius 26 cm, around which 3500 turns of a wire are wound. If the current in the wire is 11 A, what is the magnetic field (a) outside the toroid, (b) inside the core of the toroid, and (c) in the empty space surrounded by the toroid.
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A solenoid 60 cm long and of radius 4.0 cm has 3 layers of windings of 300 turns each. A 2.0 cm long wire of mass 2.5 g lies inside the solenoid (near its centre) normal to its axis; both the wire and the axis of the solenoid are in the horizontal plane. The wire is connected through two leads parallel to the axis of the solenoid to an external battery which supplies a current of 6.0 A in the wire. What value of current (with appropriate sense of circulation) in the windings of the solenoid can support the weight of the wire? g = 9.8 m s-2
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(b) What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?
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A spherical capacitor consists of two concentric spherical conductors, held in position by suitable insulating supports (Figure). Show
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An electric dipole with dipole moment 4 × 10−9 C m is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 104N C−1. Calculate the magnitude of the torque acting on the dipole.