Basic Physics Questions and Answers

1 How does reverse engineering differ from industrial espionage 2 Describe the following metrology tools scales calipers coordinate measuring machine and 3 D laser scanner Which is least expensive Which is most accurate

In Young s double slit experiment the seventh maximum with wavelength is at a distance d from central maxima and the same maximum with wavelength A is at a distance d Then d d A B C D 22 22 1 27 05 2 3 3 58

You intend to gently place several steel needles on the free surface of the water in a large tank The needle come in two lengths some are 5 cm long and some are 10 cm long Needles of each length are available with diameters of 1mm 2 5 mm and 5mm Surface tension of water 0 072 N m angle of contact is 0 and density of steel is 7 8 gm cm A All needles will float B Only 1mm diameter needles will float C Only needles with diameters 1mm and 2 5 mm will float D All needles will sink

An egg is thrown horizontally off the roof of Karunungan Bldg which is 45 meters high with an initial velocity of 8 5 s a How long does it take to hit the ground b How far does it go from the edge of the building

For the oscillation of the body in damped oscillation The amplitude of oscillation of the body decreases with time The amplitude of oscillation of the body increases with time The amplitude of oscillation of the body remains constant with time None of these

d 10 2 38 A 0 2 k2 resistor and 15 F capacitor are connected in series to a 220 V 50 Hz ac source The impedance of the circuit is a 250 2 c 29 15 2 b 268 2 d 291 52

One mole of a diatomic gas is taken through the process P T C where n and are constant If the heat capacity of gas is C R 2 then the value of n is

White light is used to illuminate the two slits in a Young s double slit experiment The separation between slits is b and the screen is at a distance d b from the slits At a point on the screen directly infront of one of the slits certain wavelengths are missing Some of these missing wavelengths are 1 b d 2 2b d 3 b 3d 210

The specific resistance p of a circular wire of radius r r R l Given r 0 24 0 02 cm R 30 1 22 and 4 80 0 01 cm The percentage error in p is nearly b 9 d 20 resistance R and lenght is given by p a 7 c 13

A hot body emits radiation which has maximum intensity at frequency Vm If the temperature of the body is doubled A the maximum intensity radiation will be at frequency 2vm B the maximum intensity radiation will be at frequency 2 C the total emitted energy per second becomes 16 times D the total emitted energy per second becomes 4 times and maximum intensity radiation will be at frequency Vm

When a mass mis hung from the lower end of a spring of negligible mass an extension x is produced in the spring The mass is set into vertical oscillations The time period of oscillation is OT 2T X mg OT 2 gx m OT 2 X 81 2 x T 27 X

In a screw gauge there are 100 divisions in circular scale and each main scale division is of 1 mm When there is no gap between the jaws 97th division coincides with the main scale zero and zero of main scale is not visible While measuring the diameter of a ball the circular scale is between 3 mm mark and 4 mm mark such that the 76th division of circular scale coincides with the reference line Select the correct alternative A the least count of the micrometer is 0 01 cm B the zero error is 0 04 mm C the diameter of the ball is 3 79 mm D the main scale reading is 4 mm

Two metal cubes A and B of same size are arranged as shown in the figure The extreme ends of the combination are maintained at the indicated temperatures The arrangement is thermally insulated The coefficient of thermal conductivity of A and B are 300 W m C and 200 W m C respectively After steady state is reached the temperature of the interface will be 100 C 1 45 C 3 30 C 2 90 C 4 60 C 0 C 23

53 An LCR series circuit is under resonance If current amplitude V is voltage amplitude R is the resistance Z is the impedance X is the inducte reactance and Xc is the capacitive reactance then V Z V V a Im c Im m Xc b I d Im XL R

What is difference in the origin of colours of a soap bubble seen in sun light and colours emerging from a prism One phenomenon is polarisation and other is dispersion The colours of soap bubble is due to diffraction and in prism it is due to dispersion The colours in prism is due to interference and in soap bubble is due to diffraction The colours of prism is due to dispersion and that of soap bubble is due to interference

8 moles of an ideal gas are present at 25 C If the pressure of the gas is increased by 100 and volume is reduced by a factor of 2 then the final temperature of the gas will be 25 K 25 C 219 C 50 C

9 As the frequency of an ac circuit increases the current first increases and then decreases What combination of circuit elements is most likely to comprise the circuit a Resistor and inductor b Resistor and capacitor c Resistor inductor and capacitor d None of these

ircular coils vn in figure Current in the then the total is 10 In an LR circuit current at t 0 is 20 A After 2s it reduces to 18 A The time constant of the circuit is in second 1 In 3 In 10 10 2 2 4 2In 10

A beam of electrons is accelerated from rest by a potential of V The de Broglie wavelength of electron is If the electrons are further accelerated by a potential of V de Broglie wavelength become The V ratio of potential difference is 112 Im

A circular cylinder of radius R and height H is filled with water to a height with constantly increasing angular speed Choose the correct alternatives H H 3 At all speeds shapes of the free surface is parabolloid 2 3 H It starts rotating about its axis The free surface touches first the brim of the cylinder and then the base of the cylinder

Three charged particles are placed at the corners of an equilateral triangle of side 1 20 m see Figure 1 The charges are Q 7 0 C Q2 9 2 C and Q3 6 3 C Figure w 07 l 1 20 m 1 20 m 1 of 1 lz Part C Calculate the magnitude of the net force on particle 2 due to the other two Express your answers using two significant figures F 0 38 N Submit Previous Answers Correct Part D Calculate the direction of the net force on particle 2 due to the other two Express your answer as positive angle using two significant figures VAX 02 65 Submit Previous Answers Request Answer

A parallel plate condenser is filled with two dielectrics as shown Area of each plate is A metre and the separation is t metre The dielectric constants are k and k2 respectively Its capacitance in farad will be A B EOA K K EOA K K t t 2 20A K K C k k Correct Answer My Answer

Two electrons are moving with same speed v One electron enters a region of uniform electric field while the other enters a region of uniform magnetic field Then after sometime if de Broglie wavelength of two electrons are 1 and 2 respectively then O A 1 O O 1 1

A beam of light consists of two types of waves with wavelengths A and 3 The number of photons passing in unit time from unit area for two wavelengths are n and 2n respectively then intensity of beam is 2 nhc 3 5 nhc 3 2 nhc 5 1

Brewster s law of polarisation follows that angle of polarisation depends on O Orientation of the plane of polarisation O Orientation of plane of vibration O Intensity of light

56 In pure Si material at a particular temperature the concentration of electron hole pairs is 1016 m It is doped with phosphorus with doping concentration of 1 ppm How many times the conductivity of the material increases due to doping It is given that concentration of Si atoms in Si material is 5 x 1028 atoms m and mobilities of electrons and holes are 0 13 m V s and 0 5 m V s respectively 1 102 3 1010 106 F C nelle 4 108

Question No 37 Single Correct A A Three 150 W 220V bulbs are connected first in parallel and then in series Each time the combination is connected to a 220 V suppl The power drawn by the combination in each case respectively will be A 450 W 50 W 50 W 450 W 100 W 3000 W 300 W 100 W Marks 4 00 18

3 The distance between the plates of a parallel plate condenser is 4mm and potential difference is 60 volts If the distance between the plates is increased to 12mm then A The potential difference of the condenser will become 180 volts B The P D will become 20 volts C The P D will remain unchanged im

A wire of length L is shaped into a circle and then bent in such a way that the two semi circles are 2iL perpendicular The magnetic moment of the system when current flows through the system is 8T then value of n is N

c 2 31 In the question number 30 the net power absorbed by the circuit in one complete cycle is 2 5 W b 10 W c 15 W d zero a 39 A C

A cylindrical piston of mass M slides smoothly inside a long cylinder closed at one end enclosing a certain mass of a gas The cylinder is kept with its axis horizontal If the piston is slightly compressed isothermally from its equilibrium position it oscillates simple harmonically the period of oscillation will be P h A Mh T 2 PA 2 1 T 271 MA Ph M

wave of wavelength 48 cm enters at S in the tube as shown in the figure Then the smallest radius r of the semicircular part so that a minimum of sound is observed at Dis S 1 14 cm 3 21 cm r D 2 20 cm 4 15 cm H

5 An ac source of voltage V V sinct is connected across the resistance R as shown in figure The phase relation between current and voltage for this circuit is a both are in phase b both are out of phase by 90 c both are out of phase by 120 d both are out of phase by 180 5 The phase relation www R V V sincor d w 19 An ic and throu a c 20 An in ac so a IC

A current carrying long wire is placed along the z axis The current is flowing along the ve z direction Find the B due to this wire at i d 0 0 v d 0 d ii 0 d 0 vi 0 d d y X iii 0 0 d vii d d d iv d d 0

29 A particle starts from rest at t 0 and moves in a straight 29 ht 0 FORTHGRET FAT3 Sos 34 and fd at 3s 1 2 ms 3 6 m s 2 3 4 1 3 line with an acceleration as shown below The velocity of the particle at t 3 sis 4x2 xy 8 4 Time s 73 2 4 ms 4 8 m s a sz 1 1 2 3 3 1 Acceleration m s 1 2 ms 3 6 m s 1 O 2 2 1 3 4 1 3 3 Time s 2 4 ms

8 The capacitance of a spherical condenser is l F If the spacing between the two spheres is 1mm then the radius of the outer sphere is A 30 cm B 6 m C 5 cm D 3 m

Q3 A nozzle is a device for increasing the velocity of a steadily flowing stream At the inlet to a certain nozzle the enthalpy of the fluid passing is 3000 kJ kg and the velocity is 60 m s At the discharge end the enthalpy is 2762 kJ kg The nozzle is horizontal and there is negligible heat loss from it a Find the velocity at exists from the nozzle b If the inlet area is 0 1 m2 and the specific volume at inlet is 0 187 m3 kg find the mass flow rate c If the specific volume at the nozzle exit is 0 498 m3 kg find the exit area of the nozzle

applied voltage d power delivered to the capacitor per cycle is zero 34 An alternating voltage in volts given by V 200 2 sin 100t is connected to 1 F capacitor through an ideal ac ammeter in series The reading of the ammeter and the average power consumed in the circuit shall be a 20 mA 0 c 20 2 mA 8 W b 20 mA 4 W d 20 2 mA 4 2 w

d infinite 20 An inductor of 30 mH is connected to a 220 V 100 Hz ac source The inductive reactance is a 10 58 2 b 12 64 02 d 22 6792 c 18 852 zero

EN 14 The maximum value of 15 A 1 In x B is 210 10 C e D For the curve y x e the point A x 1 is a point of minimum B x 0 is a point of minimum C x 1 is a point of maximum D x 0 is a point of maximum

0 Electric field lines of a portion of an electric field that is symmetrical with respect to rotation about y axis are shown in the figure A charge particles stays in equilibrium at point 0 10 If modulus of charge of the particle is changed gradually till it shifts to another equilibrium position y cm 5 0 0 estimate fractional change in the charge modulus a 1 3 a 1 0 10 b 2 3 d 8 9 x cm 5 10

Two coherent sources are separated by a distance d 2 are placed at the centre of a large circular screen arranged symmetrically as shown Ris radius of circular screen R d Light of wavelength is used in the experiment How many bright fringes will be observed on screen from A to B first quadrant Y axis S 02 B 03 Circular screen 04 S d 2 A X axis

i Two thin concentric wires shaped as circle with radii a and b lie in the same plane Allowing for a b find a Their mutual inductance b The magnetic flux through the surface enclosed by the outside wire when the inside wire carries a current I b a Figure 5 144

A particle of mass 1 kg is performing SHM and its displacement any time is given by y 2sin O T 12 6 What will be kinetic energy of particle at t 2 sec 288 144 J 70 J 288 144 70 t m

Two sources are called coherent if they produce waves O of equal wavelengths O of equal velocity O Having same shape of wave front

On introducing a thin mica sheet of small thickness in the path of one of interfering beams in YDSE O The fringe width decreases Dark fringes and bright fringes becomes of unequal width Whole fringe pattern shifts on the screen

The bob of a simple pendulum of length has a positive charge q on it The pendulum is fixed to a horizontally oriented positively charged sheet as shown in the figure The time period of the small oscillations of simple pendulum is Equal to 2 9 Less than 2 Vg Greater than 2

When white light passes through glass prism one gets spectrum on other side of the prism In the emergent beam the colour which is deviating least is O Violet ray O Red ray O Green ray

4 unchanged A block of mass m rests on a platform The platform is given up and down SHM with an amplitude d What can be the maximum frequency so that the block never leaves the platform 1 g d 3 g d 2x 2 2x g d 4 2n d g

There are two statement statement 2 points 1 When a ferromagnetic sample is subject to a cycle of magnetization then magnetizing field H lags behind the corresponding intensity of magnetization M statement 2 Materials having small coercive forces are called soft magnetic material Which option is more correct O Statement 1 Statement 2 are incorrect O Statement 1 is correct Statement 2 is incorrect O Statement 1 Statement 2 are correct Statement 1 is incorrect Statement 2 is correct