- ACurrent flowing through the coil is less
- BMagnetic field is very weak
- CPlane of coil is along the magnetic field
- ✓Coil is wound on a diamagnetic substance
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The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is
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(a) 10.6 Å |
(b) 0.53 Å |
(c) 21.2 Å |
(d) None of these |
The reading of the ammeter as per figure shown is
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(a) |
(b) |
(c) |
(d) 2 A |
.......... happens when a wave passes from one medium to another at an angle.
Electrons with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have ionization energy 72.5 keV. X-rays emitted by the tube contain only
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(a) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of ~ 0.155Å |
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(b) A continuous X-ray spectrum (Bremsstrahlung] with all wavelengths |
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(c) The characteristic X-rays spectrum of tungsten |
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(d) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of ~ 0.155Å and the characteristic X-ray spectrum of tungsten |
A conducting sphere of radius 10cm is charged 10μC. Another uncharged sphere of radius 20 cm is allowed to touch it for some time. After that if the sphere are separated, then surface density of charges, on the spheres will be in the ratio of
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(a) 1 : 4 |
(b) 1 : 3 |
(c) 2 : 1 |
(d) 1 : 1 |
If a current is passed in a spring, it
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(a) Gets compressed |
(b) Gets expanded |
(c) Oscillates |
(d) Remains unchanged |
Assertion : In a movie, ordinarily 24 frames are projected per second from one end to the other of the complete film.
Reason : The image formed on retina of eye is sustained upto 1/10 second after the removal of stimulus.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correct
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(a) Lines of force minimum but induced e.m.f. is zero |
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(b) Lines of force maximum but induced e.m.f. is zero |
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(c) Lines of force maximum but induced e.m.f. is not zero |
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(d) Lines of force maximum but induced e.m.f. is also maximum |