Two glass plates are separated by water. If surface ension of water is 75 dyne/cm and area of each plate wetted by water is 8 cm2 and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is
102 dyne
104 dyne
105 dyne
106 dyne
When a charged particle moving with velocity is subjected to a magnetic field of induction , the force on it is non- zero. This implies that
angle between is necessarily 90o
angle between can have any value other than 90o
angle between can have any value other than 180o
angle between is either zero or 180o
When power is drawn from the secondary coil of the transformer, the dynamic resistance
increases
decreases
remains unchanged
changes erratically
A.
increases
When the secondary coil circuit is open, the magnetic flux in the core is produced by the primary current only. When the secondary circuit is closed, the currents in the secondary coil also produce the magnetic flux in the core but in opposite direction. This decreases the core flux and hence reduces the back emf produced in the primary coil. The source emf is now in excess of the back emf, more current is drawn in the primary coil. Hence, the power factor is no longer zero. The power factor has increased or the phase difference is no longer 90°, ie, phase difference has decreased. Thus, dynamic resistance has increased.
What is not true for equipotential surface for uniform electric field?
Equipotential surface is flat
Equipotential surface is spherical
Electric lines are perpendicular to equipotential surface
Work done is zero
A capacitor having capacitance 1 uF with air, is filled with two dielectrics as shown. How many times capacitance will increase
12
6
8/3
3
A galvanometer having a resistance of 8 Ω is shunted by a wire of resistance 2 Ω.1f the total current is 1 A, the part of it passing through the shunt will be
0.25 A
0.8 A
0.2 A
0.5 A
The north pole of a long horizontal bar magnet is being brought closer to a vertical conducting plane along the perpendicular direction. The direction of the induced current in the conducting plane will be
horizontal
vertical
clockwise
Anticlockwise
In refraction, light waves are bent on passing from one medium to the second medium, because, in the second medium
the frequency is different
the coefficient of elasticity is different
the speed is different
the amplitude is smaller
Interference was observed in an interference chamber when air was present. Now, the chamber is evacuated and if the same light is used, a careful observation will show
no interference
interference with bright band
interference with dark bands
interference in which breadth of the fringe will be slightly increased