A conducting rod of length 2l is rotating with constant angular speed w about its perpendicular bisector. A uniform magnetic field 
exists parallel to the axis of rotation. The e.m.f. induced between two ends of the rod is
|
(a) Bω |
(b) |
(c) |
(d) Zero |
(d) Zero
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What will happen when a 40 watt, 220 volt lamp and 100 watt, 220 volt lamp are connected in series across 40 volt supply
|
(a) 100 watt lamp will fuse |
(b) 40 watt lamp will fuse |
|
(c) Both lamps will fuse |
(d) Neither lamp will fuse |
In hydrogen atom, an electron is revolving in the orbit of radius 0.53
with 6.6 
rotations/second. Magnetic field produced at the centre of the orbit is
|
(a) 0.125 |
(b) 1.25 |
(c) 12.5 |
(d) 125 |
Two charges 
and 
are placed in vacuum at a distance d and the force acting between them is F. If a medium of dielectric constant 4 is introduced around them, the force now will be
|
(a) 4F |
(b) 2F |
(c) |
(d) |
A charged water drop whose radius is 0.1 μm is in equilibrium in an electric field. If charge on it is equal to charge of an electron, then intensity of electric field will be (g = 10
|
(a) 1.61 N/C |
(b) 26.2 N/C |
(c) 262 N/C |
(d) 1610 N/C |
An AIR station is broadcasting the waves of wavelength 300 metres. If the radiating power of the transmitter is 10 kW, then the number of photons radiated per second is
|
(a) 1.5 |
(b) 1.5 |
(c) 1.5 |
(d) 1.5 |
The electric potential at a point on the axis of an electric dipole depends on the distance r of the point from the dipole as
|
(a) ∝ |
(b) ∝ |
(c) ∝ r |
(d) ∝ |
Assertion : A parallel plate capacitor is connected across battery through a key. A dielectric slab of constant K is introduced between the plates. The energy which is stored becomes K times.
Reason : The surface density of charge on the plate remains constant or unchanged.
|
(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. |
