The contribution in the total current flowing through a semiconductor due to electrons and holes are 
and 
respectively. If the drift velocity of electrons is 
times that of holes at this temperature, then the ratio of concentration of electrons and holes is
|
(a) 6 : 5 |
(b) 5 : 6 |
(c) 3 : 2 |
(d) 2 : 3 |
(a) 6 : 5
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Assertion : A bar magnet is dropped into a long vertical copper tube. Even taking air resistance as negligible, the magnet attains a constant terminal velocity. If the tube is heated, the terminal velocity gets increased.
Reason : The terminal velocity depends on eddy current produced in bar magnet.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
A lens of power +2 diopters is placed in contact with a lens of power – 1 diopter. The combination will behave like
|
(a) A convergent lens of focal length 50 cm |
|
(b) A divergent lens of focal length 100 cm |
|
(c) A convergent lens of focal length 100 cm |
|
(d) A convergent lens of focal length 200 cm |
A non-planar loop of conducting wire carrying a current I is placed as shown in the figure. Each of the straight sections of the loop is of length 2a. The magnetic field due to this loop at the point P (a,0,a) points in the direction
|
(a) |
(b) |
(c) |
(d) |
A cube of side l is placed in a uniform field E, where E = E
. The net electric flux through the cube is
|
(a) Zero |
(b) |
(c) 4 |
(d) 6 |
Ionization potential of hydrogen atom is 13.6 V.
Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be
|
(a) One |
(b) Two |
(c) Three |
(d) Four |
