A circular coil ‘A’ has a radius R and the current flowing through it is I. Another circular coil ‘B’ has a radius 2R and if 2I is the current flowing through it, then the magnetic fields at the centre of the circular coil are in the ratio of (i.e. 
to
)
|
(a) 4 : 1 |
(b) 2 : 1 |
(c) 3 : 1 |
(d) 1 : 1 |
(d) 1 : 1
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The ratio of areas within the electron orbits for the first excited state to the ground state for hydrogen atom is
| (a) 16 : 1 | (b) 18 : 1 | (c) 4 : 1 | (d) 2 : 1 |
What is the respective number of α and β particles emitted in the following radioactive decay 
|
(a) 6 and 8 |
(b) 8 and 8 |
(c) 6 and 6 |
(d) 8 and 6 |
Same current i = 2A is flowing in a wire frame as shown in figure. The frame is a combination of two equilateral triangles ACD and CDE of side 1m. It is placed in uniform magnetic field B = 4T acting perpendicular to the plane of frame. The magnitude of magnetic force acting on the frame is
|
(a) 24 N |
(b) Zero |
(c) 16 N |
(d) 8 N |
The mass defect in a particular nuclear reaction is 0.3 grams. The amount of energy liberated in kilowatt hours is (Velocity of light = 3
)
|
(a) 1.5 |
(b) 2.5 |
(c) 3 |
(d) 7.5 |
The fraction f of radioactive material that has decayed in time t, varies with time t. The correct variation is given by the curve
|
(a) A |
(b) B |
(c) C |
(d) D |
The combination of a convex lens (f = 18 cm) and a thin concave lens (f = 9 cm) is
|
(a) A concave lens (f = 18 cm) |
(b) A convex lens (f = 18 cm) |
|
(c) A convex lens (f = 6 cm) |
(d) A concave lens (f = 6 cm) |
$0$
$\delta$
$2\delta$
$3\delta$
A table tennis ball which has been covered with conducting paint is suspended by a silk thread so that it hang between two plates, out of which one is earthed and other is connected to a high voltage generator. This ball
|
(a) Is attracted towards high voltage plate and stays there |
|
(b) Hangs without moving |
|
(c) Swing backward and forward hitting each plate in turn |
|
(d) Is attracted to earthed plate and stays there |
