1 Gravitation
If the value of gravitational acceleration at a height h above the Earth's surface is the same as that at a depth d below the Earth's surface (with both h and d small compared to the Earth's radius R), then 1) h = 2 d 2) h = d 3) h = d2 / R 4) h = d / 2
2 Properties of Bulk Matter
A diving bell is to be used at great depths and so its walls are made very thick. The main reason for this is that (1) The water is much colder at great depths (2) Water pressure increases with depth of the water (3) The density of the water is much greater at great depths (4) Ice forms in deep water and could crush the bell
3 Electromagnetic Induction
An alternating voltage is connected in series with a resistance R and an inductance L. If the potential drop across the resistance is 200 volt and across the inductance is 150 volt, the applied voltage is 1) 350 volt 2) 250 volt 3) 500 volt 4) 300 volt
4 Electromagnetic Induction
A coil of circular cross-section having 1000 turns and 4cm2 face area is placed with its axis parallel to a magnetic field which decreases by 10−2Wb−m−2 in 0.01s The e.m.f. induced in the coil is: 1) 4mV 2) 0.4mV 3) 200mV 4) 400mV
Answer is D From Faraday's law, we know that $$\displaystyle E= -\dfrac{n d\phi}{dt}$$
5 Atoms and Nuclei
The electron in a hydrogen atom makes a transition n1→n2, where n1 and n2 are the principal quantum numbers of the two states. Assume the Bohr model as valid in this case. The frequency of the orbital motion of the electron in the initial state is 1 / 27 of that in the final state. The possible values of n1 and n2 are
1) n1=6,n2=3 2) n1=4,n2=2 3) n1=8,n2=1 4) n1=3,n2=1
Frequency, $$v \propto \cfrac{1}{n^3}$$ Hence, $$\cfrac{v_1}{v_2} =\cfrac{n_2 ^3}{n_1 ^3}$$ $$\cfrac{1}{27} =\cfrac{n_2 ^3}{n_1 ^3}$$ $$n_1:n_2 = 3:1$$
6 Capacitance
A circuit has a self-inductance of 1H and carries a current of 2A. To prevent sparking, when the circuit is switched off, a capacitor which can withstand 400V is used. The least capacitance of capacitor connected across the switch must be equal to
1) 50μF
2) 25μF
3) 100μF
4) 12.5μF
Energy stored in capacitor = energy stored in inductance
7 Capacitance
If the charge on an isolated capacitor remains constant while its capacitance increases:
(1) The voltage across the capacitor will increase.
(2) The voltage across the capacitor remains the same.
(3) The voltage across the capacitor will decrease.
(4) The area of the capacitor must have decreased.
8 Kinetic Theory of gases
In a mixture of ideal gases, the molecules have the same:
(1) Mean translational kinetic energy (2) Root mean square momentum (3) Speed (4) Mean speed.
9 Gravitation
.If the escape velocity of a rocket from the surface of the Earth is ve , then the escape velocity of the same rocket from the surface of a planet whose acceleration due to gravity as well as radius are 3 times that of the Earth is 1) ve 2) ve / 3 3) 3 ve 4) 9 ve
The escape velocity of an object from the surface of a planet of radius R and acceleration due to gravity g is given by Ve =Ö2gR Increasing both g and R by a factor of 3 will result in the escape velocity increasing by a factor of 3. So, the answer is 3 ve.
10 Electronic Devices
Work function for a surface is equal to :
(1) Φ = fermi energy – binding energy
(2) Φ =fremi energy
(3) Φ = binding energy – fermi energy
(4) Φ = binding energy
Your Score:
