Practice Questions

Q14.A wire elongates by ℓmm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm ) (1) ℓ/2 (2) ℓ (3) 2ℓ (4) zero

Q15.If the terminal speed of a sphere of gold (density = 19.5 kg/m3 ) is 0.2 m/s in a viscous liquid (density = 1.5 kg/m3 ) of the same size in the same liquid. (1) 0.2 m/s (2) 0.4 m/s (3) 0.133 m/s (4) 0.1 m/s

Q16.Assuming the sun to be a spherical body of radius R at a temperature of TK, evaluate the total radiant power, incident on Earth, at a distance r from the Sun. (1) R2σT4 (2) 4πr20R2σT 4 r2 r2 (3) πr20R2σT 4 (4) r20R2σT 4 r2 4πr2

Q17.The work of 146 kJ is performed in order to compress one kilo mole of gas adiabatically and in this process the temperature of the gas increases by 7∘C. The gas is (R = 8.3 J mol−1 K−1) (1) monoatomic (2) diatomic (3) triatomic (4) a mixture of monoatomic and diatomic JEE Main 2006 JEE Main Previous Year Paper

Q18.Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature T0 , while Box B contains one mole of helium at temperature (7/3)T0 . The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature. (Ignore the heat capacity of boxes). Then, the final temperature of the gases, Tf , in terms of T0 is (1) Tf = 25 T0 (2) Tf = 37 T0 (3) Tf = 73 T0 (4) Tf = 23 T0

Q19.Starting from the origin, a body oscillates simple harmonically with a period of 2 s. After what time will its kinetic energy be 75% of the total energy? (1) 12 1 s (2) 61 s (3) 14 s (4) 13 s

Q21.A coin is placed on a horizontal platform which undergoes vertical simple harmonic motion of angular frequency ω. The amplitude of oscillation is gradually increased. The coin will leave contact with the platform for the first time (1) at the highest position of the platform (2) at the mean position of the platform g2 (3) for an amplitude of g (4) for an amplitude of ω2 ω2

Q22.A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed v ms−1 . The velocity of sound in air is 300 ms−1 . If the person can hear frequencies upto a maximum of 10, 000 Hz, the maximum value of v upto which he can hear the whistle is (1) 30 ms−1 (2) 15√2 ms−1 (3) 15/√2 ms−1 (4) 15 ms−1

Q23.A string is stretched between fixed points separated by 75 cm. It is observed to have resonant frequencies of 420 Hz and 315 Hz. There are no other resonant frequencies between these two. Then, the lowest resonant frequency for this string is (1) 10.5 Hz (2) 105 Hz (3) 1.05 Hz (4) 1050 Hz

Q24.A electric dipole is placed at an angle of 30∘ to a non-uniform electric field. The dipole will experience (1) a torque only (2) a translational force only in the direction of the field (3) a translational force only in a direction normal to (4) a torque as well as a translational force the direction of the field

Q25.Two insulating plates are both uniformly charged in such a way that the potential difference between them is V2 −V1 = 20 V . (i.e. plate 2 is at a higher potential). The plates are separated by d = 0.1 m and can be treated JEE Main 2006 JEE Main Previous Year Paper as infinitely large. An electron is released from rest on the inner surface of plate 1 . What is its speed when it hits plate 2? (e = 1.6 × 10−19C, me = 9.11 × 10−31 kg) (1) 32 × 10−19 m/s (2) 2.65 × 106 m/s (3) 7.02 × 1012 m/s (4) 1.87 × 106 m/s

Q26.Two spherical conductors A and B of radii 1 mm and 2 mm are separated by a distance of 5 cm and are uniformly charged. If the spheres are connected by a conducting wire then in equilibrium condition, the ratio of the magnitude of the electric fields at the surface of spheres A and B is (1) 1 : 4 (2) 4 : 1 (3) 1 : 2 (4) 2 : 1

Q27.A material ' B ' has twice the specific resistance of ' A '. A circular wire made of ' B ' has twice the diameter of a wire made of ' A '. Then for the two wires to have the same resistance, the ratio ℓA/ℓB of their respective lengths must be (1) 2 (2) 1 (3) 1 (4) 1 2 4

Q29.In a Wheatstone's bridge, there resistances P, Q and R connected in the three arms and the fourth arm is formed by two resistances S1 and S2 connected in parallel. The condition for bridge to be balanced will be 2R (1) R (2) P = P = Q Q S1+S2 S1+S2 (3) (4) P = R(S1+S2) Q Q S1 S2 P = R(S1+S2)2 S1 S2 JEE Main 2006 JEE Main Previous Year Paper

Q30. The current I drawn from the 5 volt source will be (1) 0.17 A (2) 0.33 A (3) 0.5 A (4) 0.67 A

Q31.The resistance of a bulb filament is 100Ω at a temperature of 100∘C. If its temperature coefficient of resistance be 0.005 per ∘C, its resistance will become 200Ω at a temperature of (1) 200∘C (2) 300∘C (3) 400∘C (4) 500∘C

Q33.An electric bulb is rated 220 volt −100 watt. The power consumed by it when operated on 110 volt will be (1) 50 watt (2) 75 watt (3) 40 watt (4) 25 watt

Q35.In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a (1) circle (2) helix (3) straight line (4) ellipse

Q36.A long solenoid has 200 turns per cm and carries a current i. The magnetic field at its centre is 6.28 × 10−2 Weber /m2 . Another long solenoid has 100 turns per cm and it carries a current i/3. The value of the magnetic field at its centre is (1) 1.05 × 10−4 Weber/m (2) 1.05 × 10−2 Weber /m2 (3) 1.05 × 10−5Weber/m2 (4) 1.05 × 10−3Weber/m2 JEE Main 2006 JEE Main Previous Year Paper

Q39.In a series resonant LCR circuit, the voltage across R is 100 volts and R = 1kΩ with C = 2μF. The resonant frequency ω is 200rad/s. At resonance the voltage across L is (1) 4 × 10−3 V (2) 2.5 × 10−2 V (3) 40 V (4) 250 V

Q40.An inductor (L = 100mH), a resistor (R = 100Ω) and a battery (E = 100 V) are initially connected in series as shown in the figure. After a long time the battery is disconnected after short circuiting the points A and B. The current in the circuit 1 mm after the circuit is (1) 1 A (2) 1/eA (3) e A (4) 0.1 A

Q41.The rms value of the electric field of the light coming from the Sun is 720 N/C . The average total energy density of the electromagnetic wave is (1) 3.3 × 10−3 J/m3 (2) 4.58 × 10−6 J/m3 (3) 6.37 × 10−9 J/m3 (4) 81.35 × 10−12 J/m3

Q44.The threshold frequency for a metallic surface corresponds to an energy of 6.2eV , and the stopping potential for a radiation incident on this surface 5 V . The incident radiation lies in JEE Main 2006 JEE Main Previous Year Paper (1) X-ray region (2) ultra-violet region (3) infra-red region (4) visible region

Q45.The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows : (1) (2) (3) (4)

Q46.An alpha nucleus of energy 1 mv2 bombards a heavy nuclear target of charge Ze. Then the distance of closest 2 approach for the alpha nucleus will be proportional to (1) 1 (2) v2 Ze (3) 1 (4) 1 m v4