For a given plate-voltage, the plate current in a triode is maximum when the potential of
|
(a) The grid is positive and plate is negative |
(b) The grid is positive and plate is positive |
|
(c) The grid is zero and plate is positive |
(d) The grid is negative and plate is positive |
(b) The grid is positive and plate is positive
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A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is
|
(a) The focal point shifts away from the lens by a small distance |
|
(b) The focus remains undisturbed |
|
(c) The focus shifts to infinity |
|
(d) The focal point shifts towards the lens by a small distance |
A magnet of magnetic moment 50 
is placed along the x-axis in a magnetic field 
T. The torque acting on the magnet is
|
(a) 175 |
(b) 150 |
(c) 75 |
(d) 25 |
If a source is transmitting electromagnetic wave of frequency 8.2 
Hz, then wavelength of the electromagnetic waves transmitted from the source will be
|
(a) 36.6 m |
(b) 40.5 m |
(c) 42.3 m |
(d) 50.9 m |
The intensity of electric field required to balance a proton of mass 1.7 
and charge 1.6 
is nearly
|
(a) |
(b) 1 |
(c) 1 |
(d) 1 |
Two long straight wires are set parallel to each other. Each carries a current i in the same direction and the separation between them is 2r. The intensity of the magnetic field midway between them is
|
(a) |
(b) 4 |
(c) Zero |
(d) |
Specific rotation of sugar solution is 0.01 SI units. 200 
of impure sugar solution is taken in a polarimeter tube of length 0.25m and an optical rotation of 0.4rad is observed. The percentage of purity of sugar is the sample is
|
(a) 80% |
(b) 89% |
(c) 11% |
(d) 20% |
