| PRACTICE PAPER IIT-JEE PHYSICS– 2007 |
| - Test duration is 2 hours. |
Single Option Question
1.A source of emf E = 10 V and having negligible internal resistance is
connected to a variable resistance. The resistance varies as shown in Figure. The total charge that has passed through the resistor R during the time interval t1 to t2 is |
 |
| (A) |
40 loge4 |
(B) |
30 loge3 |
| (C) |
20 loge2 |
(D) |
10 loge2 |
| 2. A cylindrical tube contains two ideal gases with equal masses. The molar masses of the gas are M1M= 32 and M2 = 28 respectively. The gases are seperated by one movable partition A and another fixed partition B as shown in Figure. The movable partition can move freely without friction inside the cylinder. The ratio of the heights of the gases inside the cylinder in equilibrium is |
 |
| (A) |
0.875 |
(B) |
1.143 |
(C) |
0.9 |
(D) |
0.6 |
3. Two masses m1 and m2 initially infinite distance apart are at rest. Then velocities of approach when the seperation between them becomes r, is given by v1 = km2 and v2 = km1 respectively. If k is a constant for a given distance r, then the value of k is
4. One end of a string of length L is tied to the ceiling of a lift accelerating upwards with an acceleration g/2. The linear mass density of the string is  (x) = 0 x1/2 where, x is measured from the bottom. The time taken by a pulse to reach from bottom to top is
5. The number of emission lines of atomic hydrogen spectrum between 400 nm to 700 nm according to Bohr' s theory is
6. A lake is lit by an under water isotropic lamp. The refractive index of water is 4/3. If the surface of the lake is covered by a layer of refractive index  ,
the fraction of light totally internally reflected at water-oil surface is (Assume that the lake is absolutely calm and that both the oil and water are 100% transparent).
| (A) |
0.25 |
(B) |
0.5 |
(C) |
0.75 |
(D) |
1 |
Multiple Option Question
| 7. The Figure shows the displacement of a particle going along the x-axis as a function of time. The force acting on the particle is zero in the region. |
 |
| (A) |
AB |
(B) |
BC |
| (C) |
CD |
(D) |
DE |
8. Seven identical rods of material of thermal conductivity k are connected as shown in Figure. All the rods are of identical length l and cross section area A. If the one end B is kept at 100oC and the other end is kept at 0oC, what would be the temperature of the junctions C, D and E ( C, D and E) in the steady state? |
 |
(A)C > E > D
(B) E = 50oC and D = C
(C) E = 50oC, C = 62.5oC and D = 37.5oC
(D) E = 50oC, C = 60oC and D = 40oC
| 9. In the circuit shown the potential difference across 3 F capacitor is V and the equivalent capacitance between A and B is CAB? |
 |
| (A) |
CAB = 4 F |
(B) |
CAB =  F |
| (C) |
V = 20 V |
(D) |
V = 40 V |
10. A thin biconvex lens with their radius of curvature 20 cm and 30 cm is placed with its principal axis first along a beam of parallel red light and then along a beam of parallel blue light. If the local length for the mean colour is 23.1 cm, B = 1.528 and B = 1.504, the seperation of foci for red and blue light is  f. The dispersive power of the material of the lens is  . Then
| (A) |
f = 1.08 cm |
(B) |
f = 2.16 cm |
(C) |
= 0.47 |
(D) |
= 0.047 |
| Take |
 |
PASSAGE
The techniques of solving the motion of a body with respect to a non-inertial frame of reference is by introducing the concept of PSeudo forces.
Suppose a frame of reference S' moves with constant acceleration  0 with respect to an inertial frame S. The acceleration of the particle P measured with respect to S' is PS' and that with respect to S is PS. The acceleration of S' with respect to S is S'S = 0
Since S' is translating with respect to S, we have
PS = PS' - S'S
= PS' - SS'
or = PS - 0
m = mPS - m0 where m is the mass of the particle.
|
 |
Since S is an inertial frame mPS is equal to the sum of all the forces acting on P. Writing this sum as  , we get m = - m0
This equation relates the acceleration of the particle and forces acting on it. Comparing it with equation = m where acceleration is measured in an inertial frame the acceleration of frame with respect to an inertial frame comes into the equation. Newton' s law  is not valid for such non-inertial frame. An extra term - m has to be added to the sum of the forces acting on the particle before using the equation. It can be noted that in this extra term m is the mass of particle under cosideration and is the acceleration of working frame reference with respect to the inertial frame. We are so familiar with Newton' s laws that we would like to use the same equation for this frame also. This can be done if we call (- m) a force acting on the particle. Then while preparing the list of forces acting on the particle. We include all real forces acting on P and include an imaginary force - m this is called pseudoforce. This force is to be included because we are discussing the motion from a non-inertial frame and still want to use Newton' s law.
11. A body of mass m is placed over a smooth inclined plane of inclination , which is placed over a lift which is moving up with an acceleration a0. Base length of the inclined plane is L. Calculate the velocity of the block with respect to lift at the bottom. If it is allowed to slide down from the top of the plane from rest.
| 12. A particle of mass m is placed on the smooth face of an inclined plane of mass M and slope which is free to slide on a smooth horizontal plane in a direction perpendicular to the edge. If the particles slides with an acceleration 'a', the acceleration of the inclined plane towards right A will be |
 |
13. A ball is suspended on a thread from the ceiling of a car. The brakes are applied and the speed of car changes from 5 m/sec to 5/3 m/sec during the time interval of 3 seconds. Find the angle that the thread with the ball will deviate from vertical ? Take g = 10 m/sec2.
PASSAGE
The rate at which sun radiates is 39 x 1026 W. All the radiated energy is generated by the proton-proton cycle.
14. In each proton-proton cycle, the number of protons used is
15. If m(1H1) = 1.007825 u, m (4He2) = 4.002603 u the energy released in the proton-proton cycle is nearly (1 u = 981.5 MeV)
| (A) |
26.7 eV |
(B) |
26.7 MeV |
(C) |
2.67 eV |
(D) |
2.67 MeV |
16.The rate at which hydrogen is being consumed in the core of sun is
| (A) |
3.05 x 1011 kg/s |
(B) |
6.1 x 1011 kg/s |
| (C) |
3 x 105 kg/s |
(D) |
6.1 x 105 kg/s |
Subjective Question
17. A circuit draws a power of 550 W from a source of 220 V/50 Hz. The power factor of the circuit is 0.8 and the current lags in phase behind the voltage. To make power factor 1, what capacitance is to be connected in the circuit? Express answer in microfarads.
18. A hollow steel sphere, weighing 200 kg is floating on water. A weight of 10 kg is to be placed on it in order to submerge when the temperature is 20oC. How much less weight is to be placed when temperature increases to 25oC? Express the weight in grams.
Match the following (with only one choice correct)
| 19. |
Column 1 |
|
Column 2 |
| (A) |
Capacitance |
(P) |
C2J-1 |
| (B) |
Inductance |
(Q) |
NA-1m-1 |
| (C) |
Magnetic Induction |
(R) |
VsA-1 |
| (D) |
Special Resistance |
(S) |
 .m |
| 20. |
Column 1 |
|
Column 2 |
| (A) |
Interference |
(P) |
Colours in peacock feathers |
| (B) |
Diffraction |
(Q) |
Spherical wavefront |
| (C) |
Point source |
(R) |
Huygen's principle |
| (D) |
Secondary wavelets |
(S) |
Study of crystal structure |
|
|
You need to be logged in for the answers!
|
