Experiments Questions and Answers

33 A great physicist of this century P A M Dirac loved playing with numerical values of Fundamental constants of nature This led him to an interesting observation Dirac found that from the basic constants of atomic physics c e mass of electron mass of proton and the gravitational constant G he could arrive at a number with the dimension of time Further it was a very large number its magnitude being close to the present estimate on the age of the universe 15 billion years From the table of fundamental constants in this book try to see if you too can construct this number or any other interesting number you can think of If its coincidence with the age of the universe were significant what would this imply for the constancy of fundamental constants

44 A transistor cannot be used as a 1 Amplifier 2 Oscillator 3 Modulator 4 Rectifier

When a magnet is pushed in and out of a circular coil C connected to a very sensitive galvanometer G as shown in the adjoining diagram with a frequency then N S 1 Constant deflection is observed in the galvanometer 2 Visible small oscillations will be observed in the galvanometer if is about 50 Hz 3 Oscillations in the deflection will be observed clearly if or 2 Hz 4 No variation in the deflection will be seen if or 2 Hz

units find the value of the current at t 5 s An electron gun emits 2 0 10 An electron gun emits 2 0 x 10 16 electrons per second What electric current does this correspond to

An ideal monostomic gas is confined in a horizontal cylinder by a spring loaded piston as shown in figure Initially the gas is at temperature T pressure P and volume V and the spring is in its felax state the gas is then heated very slowly to temperature T pressure P and volume V During m process the piston moves out by a distance x Ignoring the friction between the piston and the cylinds the correct statement s is are JEE Advanced 2015 P 2 4 88 23 A IT V 2V and T 3T then the energy stored in the spring is P V B If V 2V and T 3T then the change in internal energy is 3P V C IV 3V and T 4T then the work done by the gas is D If V 3V and T 4T then the heat su the gas is 17 RY

inch 8 In a vernier callipers main scale divisions are in inches Each inch division has eight small divisions of each 8 divisions of vernier scale are equal to 7 divisions of main scale While measuring the length of a rod callipers shows the reading as follows What is the length of rod A 75 64 inch 77 C 64 inch B 76 64 inch D None of these 1 inch www 2 Vernier scale Main scale

The value of e me can be obtained by using a specially designed vacuum tube The figure contains a heated filament F and an anode A which is maintained at a positive potential relative to the filament by a battery of known voltage V Electrons get emitted from the heated filament and are accelerated towards the anode which has a small hole in the centre for the electrons to pass through into a region of constant magnetic field B which points into the plain of the paper The electrons then move in a semicircle of diameter d hitting the detector cathode as shown Prove that me 8V B d B F d

5 A physical quantity X is related to four measurable quantities a b c and d as given X a2 b c5 2 d 2 The percentage error in the measurement of a b c and d are 1 2 2 and 4 respectively What is the percentage error in quantity X a 15 b 17 c 21 d 23

The displacement of an oscillating particle is given by x asinot bcos t where a b and are constants Prove that the particle performs a linear S H M with amplitude A a b 2

A student performs experiment with simple pendulum and measures time for 10 vibrations If he measures the time for 100 vibrations the error in the measurement of time period will be reduced by a factor of a 10 b 90 c 100 d 1000

of error measurement of physical quantities A B C and D are 1 2 3 and 4 respectively Then the maximum percentage of error in the measurement X 2 bns A B 2 2 where Y will be In an experiment the percentage occurred in the

Suppose all the electrons of 100 g water are lumped together to form a negatively charged particle and all the nuclei are lumped together to form a positively charged particle If these two particles are placed 10 0 cm away from each other find the force of attraction between them Compare it with your weight

X HP N vin Y Bar magnet Poles of magnet

Regular Medical 2 a point has simultaneous velocities represented by u 2u 3 3u and 4u The angle between the first and second the second and third and the third and fourth are respectively 60 90 and 150 The angle the resultant velocity makes with u is 1 120 2 60 3 150 4 30 14

INTRODUCTORY EXERCISE 3 4 1 A student performs an experiment to determine Young s modulus of a wire exactly 2 m long by Searle s method In a particular reading the student measures the extension in the length of the wire to be 0 8 mm with an uncertainty of 0 05 mm at a load of 1 0 kg The student also measures the diameter of the wire to be 0 4 mm with an uncertainty of 0 01 mm Take of elasticity with limits of error

If P Q R 0 PI 2 Q1 and R 2121 then the angle between R and P is 1 COS 3 tan 1 5 4 2 1 2 2 4 sin 1 tan 3 4 2 5 4 2