Explanation:
According to the first law of limiting friction,
$\text{f}=\mu\text{N}$
where f is the frictional force
N is the normal reaction force
$\mu$ is the coefficient of static friction
and
$\text{N = mg}-\text{F}\cos\theta$
where m is the mass of the body
F is the contact force acting on the body
If we decrease the angle between this contact force and the vertical, then $\text{F}\cos\theta$ increases and the normal reaction force (N) as well as the frictional force (f) decrease.
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At a certain place the angle of dip is 30° and the horizontal component of earth's magnetic field is 0.50 Oersted. The earth's total magnetic field is
(a) 
|
(b) 1 |
(c) 
|
(d) 
|
A vertical wire carrying a current in the upward direction is placed in horizontal magnetic field directed towards north. The wire will experience a force directed towards
|
(a) North |
(b) South |
(c) East |
(d) West |
Function of rectifier is
|
(a) To convert ac into dc |
(b) To convert dc into ac |
|
(c) Both (a) and (b) |
(d) None of these |
The photoelectric threshold wavelength for a metal surface is 6600 Å. The work function for this is
|
(a) 1.87 V |
(b) 1.87 eV |
(c) 18.7 eV |
(d) 0.18 eV |
Which of the following statements is true for an N-type semi-conductor
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(a) The donor level lies closely below the bottom of the conduction band |
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(b) The donor level lies closely above the top of the valence band |
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(c) The donor level lies at the halfway mark of the forbidden energy gap |
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(d) None of above |