# IIT JEEE Physics - 1985

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### IIT JEE –Past papers:

IIT JEE –Past papers PHYSICS- UNSOLVED PAPER - 1985

### SECTION – I:

SECTION – I Single Correct Answer Type In each of the statements below, several alternatives are given. In some cases more than one alternative is correct. Select the correct alternative (s) in each case and write down the corresponding letters(s) (a) (b)(c) or (d) in your answer book. For each part, marks will be awarded only if ALL the correct alternatives are selected.

### Problem:

01 A uniform chain of length L and mass M is lying on a smooth table and one-third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity , the work required to pull the hanging part on to the table is : MgL MgL /3 MgL /9 MgL /18 Problem

### Problem:

Problem 02 A mass M is moving with a constant velocity parallel to the X-axis. Its angular momentum with respect to the origin: Is zero Remains constant Goes on increasing Goes on decreasing

### Problem:

Problem 03 An air column in a pipe, which is closed at one end, will be in resonance with a vibrating tuning fork of frequency 264 Hz if the length of the column in cm is: 31.25 62.50 93.75 125

### Problem:

Problem 04 70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30 0 C to 35 0 C .The amount of heat required ( in calories) to raise the temperature of the same gas through the same range (30 0 C to 35 0 C0 at constant volume is: 30 50 70 90

### Problem:

Problem 05 A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively , this region of space may have: a. E = 0, B = 0 b. c. E 0, B = 0 d. E 0, B 0

### Problem:

Problem 06 A Parallel plate air capacitor is connected to a battery. The quantities charge, voltage, electric field and energy associated with this capacitor are given by respectively. A Dielectric slab is now introduced to fill the space between the plates with the battery still in connection. The corresponding quantities now given by Q, V E and U are related to the previous one as : Q > Q 0 V > V 0 E > E 0 U > U 0

### Problem:

Problem 07 For a given plate voltage, the pate current in a triode valve is maximum when the potential of : The gird is positive and plate is negative The gird is zero and plate is positive The grid is negative and plate is positive The gird is positive and plate is positive

### Problem:

Problem 08 A rectangular loop carrying a current I is situated near a long straight wire such that the wire is parallel to one of the sides of the loop and is in the plane of the loop (Fig. 1985.1.). If a steady current I is established in the wire as shown in Fig. 1985.1, the loop will: Rotate about an axis parallel to the wire Move away from the wire Move towards the wire Remain stationary

### Problem:

Problem 09 The X-ray beam coming from an X-ray tube will be: Monochromatic Having all wavelengths smaller than a certain maximum wavelength Having all wavelengths larger than a certain minimum wavelength Having all wavelengths lying between a minimum wavelength

### Problem:

Problem 10 The spring balance A reads 2 kg with a block m suspended from it (Fig. 1985.2.) A balance B reads 5 kg when a beaker with liquid is put on the pan of the balance. The two balances are now so arranged that the hanging mass is inside the liquid in the beaker as shown in Fig. 1985.2. In this situation. The balance A will read more than 2kg The balance B will read more than 5 kg The balance A will read less than 2 kg and B will read more than 5 kg the balance A and B will read 2 kg and 5 kg and 5 kg respectively

### SECTION – II:

SECTION – II Fill in the blanks Read the following statements carefully. Indicate the sub-division number and write down the matter corresponding to each blank strictly in the order in which it appears in the statement.

### Problem:

01 In the Uranium radioactive series the initial nucleus is U and the final nucleus is When the U radium nucleus decays to Lead, the number of particles emitted is ______________ and the number of - particles emitted is __________. Problem

### Problem:

Problem 02 A convex lens A of focal length 20 cm and a concave lens B of focal length 5 cm are kept along the same axis with a distance d between them. If a parallel beam of light falling on A leaves B as a parallel beam, then d is equal to ______________ cm.

### Problem:

Problem 03 Planck’s constant has the dimensions __________________.

### Problem:

Problem 04 According to Keller's second law, the radius vector to a planet from the sun sweeps out areas in equal intervals of time. This law is a consequence of the conservation of _________________.

### Problem:

Problem 05 The variation of temperature of a material as heat is given to it at a constant rate is shown fig. 1985.3. The material is in solid state at the point O. The state of the material at the point P is _____________.

### Problem:

Problem 06 A monochromatic beam of light of wavelength 6000Å in vacuum enters a medium of refractive index 1.5. In the medium its wavelength is ________________, its frequency is ___________________.

### SECTION – III:

SECTION – III Each of which either true or False State whether the following statements are TRUE or FALSE, giving V towards a wall and an observer is stationary between the source and the wall. When the observer is between the source and the wall he will hear beats.

### Problem:

01 A Source of sound with frequency 256 Hz is moving with a velocity v towards a wall and an observer is stationary between the source and the wall. When the observer is between the source and the wall he will hear beats. Problem

### Problem:

02 The current-voltage graphs for a given metallic wire at two different temperatures and are shown in Fig. 1985.4. The temperature is greater than. Problem

### Problem:

Problem 03 Two identical trains are moving on rails along the equator on the earth in opposite directions with the same speed. They will exert the same pressure on the rails.

### Problem:

Problem 04 The curves A and B in Fig. 1985.5 show P-V graphs for an isothermal and an adiabatic process for an ideal gas. The isothermal process is represented by the curve A.

### Problem:

Problem 05 An electron and a proton are moving with the same kinetic energy along the same direction. When they pass through a uniform magnetic field perpendicular to the directions of their motion, they describe circular paths of the same readies.

### Problem:

Problem 06 A triangular plate of uniform thickness and density is made to rotate about an axis perpendicular to the plane of the paper and (a) passing through A and (b) passing though B, by the applications of the same force, F at C (midpoint of AB) as shown in Fig. 1985.6. The angular acceleration in both the cases will be the same.

### Slide 27:

FOR SOLUTION VISIT WWW.VASISTA.NET 