Basic Physics Questions and Answers

26 A cubical region of space is filled with some uniform electric and magnetic field An electron enters the cube across one of its faces with velocity v and a positron enters via opposite face with velocity v At this instant which one of the following is not correct a The electric forces on both the particles cause identical accelerations b The magnetic forces on both the particles cause equal acceleration c Both particles gain or loose energy at the same rate d The motion of the centre of mass is determined by B alone

21 Identify the correct definition 1 If after every certain interval of time particle repeats its motion then motion is called periodic motion 2 To and fro motion of a particle over the same path about its mean position in certain time interval is called oscillatory motion 3 Oscillatory motion described in terms of single sine and cosine functions is called simple harmonic motion 4 All of these

70 Two coils A and B having turns 300 and 600 respectively are placed near each other on passing a current of 3 0 ampere in A the flux linked with A is 1 2x104 weber and with B it is 9 0 10 5 weber The mutual inductance of the system is MP PMT 2001 tap a 2x 10 5 henry c 4 10 5 henry b 3 x 105 henry d 6 x 10 5 henry

24 Five balls marked a to e are suspended using separate threads Pairs b c and d e show electrostatic repulsion while pairs a b c e and a e show electrostatic attraction The ball marked a must be 1 Negatively charged 2 Positively charged 3 Uncharged 4 Any of the above is possible

1 The least count of a stop watch is 5 s The time of 20 oscillations of a pendulum is measured to be 25s What is the maximum percentage error in this meas urement 1 8 2 1 3 0 8 4 16 The refractive index of water measured by the relation

17 Select the correct statement for work heat and change in internal energ 1 Heat supplied and work done depend on initial and final states 2 Change in internal energy depends on the initial and final states only 3 Heat and work depend on the path between the two points 4 All of these

A charged metallic bob of mass m and charge Q is in equilibrium in presence of electric repulsion by Q fixed as shown in fig Find Q 60 L L fixed 1 2 mg L 2 4 mg L 3 8 mg L 4 None

29 A proton and an a particle enter in a uniform magnetic field perpendicularly with same speed The ratio of time periods of both particle will be c 2 1 a 1 2 b 1 3 30 A proton a douters d 3 1

3 A charged particle would continue to move with a constant velocity in a region wherein which of the following conditions is not correct b E 0 B 0 d E 0 B 0 a E 0 B 0 c E 0 B 0

Two simple pendulums are suspended from the same point using identical ideal non conducting string and when supplied with identical charges to the bobs they get deflected and attain equilibrium with the angle between strings as 120 If the pendulum system is kept in a liquid o density equal to th of density of the bob the angle between the two strings is halved The dielectric constant of the liquid is

1 An electron having momentum 2 4 x 10 23 kg m s enters a region of uniform magnetic field of 0 15 T The field vector makes an angle of 30 with the initial velocity vector of the electron The radius of the helical path of the electron in the field shall be 3 a 2 mm b 1 mm c mm d 0 5 mm

A 2 F capacitor C is first charged to a potential difference of 10 V using a battery Then the thong battery is removed and the capacitor is methongo connected to an uncharged capacitor C of 8uF mathango The charge in C on equilibrium condition C Round off to the Nearest mothongo 15 mathongo mathonge mash mathongo mathonge math mathongo mathongs math mathongo mathongs maths

16 A charged particle is moving on circular path with velocity v in a uniform magnetic field B if the velocity of the charged particle is doubled and strength of magnetic field is halved then radius becomes

period z m k U A block of mass m is suspended from the ceiling of a stationary standing elevator through a spring of spring constant k Suddenly the cable breaks and the elevator starts falling freely Show that the block now executes a

following is true We can find mass of photon by p mv Rest mass of photon is not zero Cut off stopping voltage or is independent of frequency Threshold wavelength depends upon

40 Which of the following statements is wrong 1 bimetal is used in metal thermometers 2 bimetal is used in thermostal for regulating 3 bimetal relays are used to open or close 4 bimetal are used to generate electricity

0 The relation between an ac voltage source and time in SI units is V 120 sin 100 t cos 100 t V The value of peak voltage and frequency will be respectively a 120 V and 100 Hz c 60 V and 200 Hz 120 b V and 100 Hz d 60 V and 100 Hz

31 A loop of irregular shape made of flexible conducting wire carrying clockwise current is placed in uniform inward magnetic field such that its plane is perpendicular to the field Then the loop 1 Experiences force 2 Develops induced current for a short time 3 Changes to circular loop 4 All of these

the figure shown a cart moves on a smooth horizontal surface with a constant velocity v acted upon by an external nstant force of magnitude F Sand falls on to the cart with negligible velocity at constant rate u kg s and sticks to the cart nd N if the power supplied by external agent applying the force F is vN M F

An infinitely long line charge having a uniform charge per unit length A lies a distance d from poin O as shown in Figure Determine the total electric flux through the surface of a sphere of radius A centered at O resulting from this line charge R d 2 R d AR A C A R d 28 B D 4 22 R d

A parallel plate capacitor has plate area 100 m and plate separation of 10 m The space between the plates is filled up to a thickness 5 m with a material of dielectric constant of 10 The resultant capacitance of the system mathon mathongo mathenge is x pF The value of eo 8 85 x 10 12 F m 1 The value of x to the nearest integer is mathongo

Two vectors of equal magnitude 5 unit have an angle 60 between them Find the magnitude of a the sum of the vectors and b the difference of the vectors to A B A Figure 2 7 B B 60 120 D 17 100t A

A sample of hydrogen gas in its ground state is irradiated with photons of 10 2 eV energies The radiation from the above sample is used to irradiate two other samples of excited ionized Het and excited ionized Li respectively Both the ionized samples absorb the incident radiation How many spectral lines are obtained in the spectra of Li A B 10 15 Correct Answer 20

In the arrang shown in the figure the string is light and inextensible and friction is absent everywhere Find the speed of both the blocks after the block A has ascended a height of Given that and Take 1 m m 1 kg MA mg 2 kg mB g 10 m s

ma A particle of mass m moves in a circular orbit in a central potential field U r Uor4 If Bohr s quantizatio conditions are applied radii of mathango possible orbitals ru vary with n a where a is mothongu mathongo mathongo mathongo mathongomathongo mathan

20 Which of the following material is most suitable for cooking utensil 1 Low conductivity and low specific heat 2 High conductivity and low specific heat 3 Low conductivity and high specific heat 4 High conductivity and high specific heat

The following measurements were made over a lake Incoming shortwave radiations R 400 Wm surface albedo a 0 25 air temperature T 15 C lake surface temperature T 20 C relative humidia RH 70 a Find the net radiation at the surface of the lake What is the dew point temperature of the air Useful Data TABLE 3 1 TYPICAL BROADBAND EMISSIVITY FOR VARYING LAND SURFACE TYPES FROM ARYA 2001 SURFACE TYPE Water Snow old Snow fresh Ice Bare soil Grass long 1 m Grass short 0 02 m Agricultural crops Forests EMISSIVITY 0 92 0 97 0 82 0 89 0 90 0 99 0 92 0 97 0 84 0 97 0 90 0 95 0 90 0 99 0 97 0 99

The atomic hydrogen emits a line spectrum consisting of various series Which series of hydrogen atomic mathangamathongo mathongs mathongs spectra is lying in the visible region mathongo 1 Brackett series 2 Paschen series mathongo mathongo

Your physics assignment is to figure out a way to use electricity to launch a small 6cm long plastic stirrer You decide that you will charge the little plastic rod by rubbing it fur then hold it near a long charged wire When you let go the electric force of wire on the plastic rod will shoot it away Suppose you can uniformly charge the plastic stirrer to 10nC and that the linear charge density of the long wire is 10 7 C m The mass of plastic stirrer is 1kg OM 12 The electric force on the plastic stirrer if the end closest to the wire is 2cm away is A 4 2 10 N B 2 8 10 N C 1 4 10 N D 8 5 x 104N

A charged parallel plate capacitor of distance d has U energy A slab of dielectric constant K and thickness d is then introduced between the plates of the capacitor The new energy of the system is given by 1 KU 2 K U 3 U 4 5

A particle of mass 1 kg is taken along the path ABCDE from A to E see figure The two hills are of heights 50 m and 100 m and the horizontal distance AE is 20 m while the path length is 400 m The coefficient of friction of the surface is 0 1 Take g 10 ms and 3 1 73 the minimum work on the masses required to accomplish this is A 20 J A B 173 J B C E C 400 J D O J

A boy wants to write the number in each field of the figure shown in the image Each number is the sum of the numbers in the neighbor fields neighbor fields are all fields that touch What number is going to be written in the middle field

Two semicircular rings having same mass m and radius r are joined as shown in the figure The moment of inertia of the system about an axis passing through the centre of mass of the system and perpendicular to the plane of the figure is

A composite rod is made by joining two rods of ifferent materials and of same cross section If 12 are their initial lengths at t C then a the increase in length of composite rod at 12 C A1 4 1 1 12 41 given by The effective coefficient of linear expansion of

15 Three boys are pushing horizontally a box placed on horizontal table One is pushing towards north with a 5 3N force The second is pushing towards east and third pushes with a force 10 N such that the box is in equilibrium Find the magnitude of the force second boy is applying in newton UD0015 Scalar product of vectors 16 UD0016 Consider the two vectors L l 23 3k and 7 41 5j 6k Find the value of the scalar a such that the vector L al is perpendicular to L

If an electron is moving in the nth orbit of the hydrogen atom then its velocity vn for the nth orbit is given as mathongo mathongo 1 V x n 2 V x 3 V X n 4 V x mathongo mathongs mathongo mathongo mathongo mathongo mathongo moth

If electron of hydrogen atom is replaced by another particle of same charge but of double mass then O Bohr s radius will increase M lonisation energy of atom will be doubled Speed of new particle in given state will be lesser than electrons speed in same orbit Gap between energy levels will now be doubled

Which of the following is null vector A Velocity vector of a body moving in a circle with a uniform speed B Position vector of the origin of the rectangular co ordinate system C Velocity vector of a body moving in a straight line with a uniform speed D Displacement vector of a stationary object

The current required to be passed in a solenoid of length 10 cm and number of turns 100 so that the magnet gets demagnetized when inside the solenoid is 3A The coercivity of a small magnet where the ferromagnet gets demagnetized is nx 10 A m Find the value of n

An open container 2 x 2 base x 2m height half full with water is accelerated at 4 m S up a 15 incline take g 10 m sec Choose correc option water will not spill for given acceleration at acceleration 7 05 m s 1 the water begin to spill at acceleration 7 05 m s 1 the water doesn t spill water will spill for given acceleration

3 An ideal mono atomic gas is confined in a cylinder with the help of a piston that can slide inside the cylinder without friction Walls of the cylinder have finite conductivity Initially the piston is in equilibrium with its external surface exposed to the atmosphere at pressure 105 Pa A transient pulse of heat is injected into the cylinder through its walls causing the gas to expand until its volume changes by 0 2 L How much heat was supplied by the pulse a 20 J c 50 J b 30 J d 60 J

Some white colourless crystals are heated A cracking sound is heard and brown fumes are given off and the residue left is yellow brown in colour When a glowing splinter is held in the fumes it is relighted The fumes consist of A 0 C Cl B NO D NO and O

and the other same surface contact and face charge 5 An object flying in air with velocity 20 251 12k suddenly breaks in two pieces whose masses are in the ratio 1 5 The smaller mass flies off with a velocity 100 351 8k The velocity of the larger piece will be 1 4 23 16k 2 00 15 201 2 1001 351 8k 30 15 901

A truck is stationary and has a bob suspended by a light string in a frame attached to the truck The truck suddenly moves to the right with an acceleration of a The pendulum will tilt 1 to the left and angle of inclination of the pendulum with the vertical is sin 9 9 a 2 to the left and angle of inclination of the pendulum a g 3 to the left and angle of inclination of the pendulum with the vertical is tan 1 a with the vertical is sin g 4 to the left and angle of inclination of the pendulum with the vertical is tan 1 g

8 A current of 6 A enters one corner Pof an equilateral triangle PQR having 3 wires of resistances 2 12 each and leaves by the corner R Then the currents I and I are a 2 A 4 A b 4 A 2 A c 1 A 2 A d 2 A 3 A 20 76A ww 252

Two 2 0 cm diameter insulating spheres have a 6 00 cm space between them One sphere is charged to 57 0 nC the other to 41 0 nC What is the electric field strength at the midpoint between the two spheres

If temperature area changed by a factor of changes by a factor 8 of a body is increased by a factor of 2 and 113 2 4 then the power radiated

7 Four resistors are connected as shown in the figure A 6 V battery of negligible resistance is 30 is connected across terminals A and C The potential difference across terminals B and D will be a Zero b 1 5 V c 2V d 3 V 100

c 40 2 and 30 32 63 An infinite ladder network of resistances is constructed with 122 and 2 2 resistance as shown in figure The 6 V battery between A and B has negligible internal resistance The equivalent resistance between A and B is 192 19 6V 192 ww 20 20 B a 192 b 22 292 192 c 392 2923 d 492 Qas

U B 1 Two identical thin rigid rods AB and CD each of length L touching each other at point P rotate in a plane about their stationary ends A and C that are a distance h apart Velocities of their ends B and D have constant moduli v and v respectively Find component of velocity of their point of intersection P along the rod AB when the rods make angles a and with the line AC