Basic Physics Questions and Answers

A 100 volts voltmeter whose resistance is 20 k2 is connected in series with a very high resistance R When it is joined across a line of 110 volts it reads 5 volts What is the magnitude of resistance R

An electromagnetic wave going through vacuum the electric and magnetic field of wave is described by E Eosin kx wt B Bosin kx wt Which of the following equation is true Eok Bow Eow Bok Eo Bo wk O E hr min k Bo

A transformer is used to light a 50 W 110 V lamp from 220 mains If main current is 0 25 A efficiency of transformer is 91 95

In an AC circuit 100 sin 200 nt The minimum time required for the current to achieve its peak value from 0 will be 100 200 1 300 100 S S S S

Motion in combined electric and magnetic 33 A charge q mass m moving with velocity v enters region of magnetic field B as shown in diagram Assumin magnetic field to be constant within corresponding region find deviation of charge and time spent in it the charge a m q v B b 0 m q v B m q v BO X

A potential difference of 10 V is applied across a conductor of length 5 cm If drift velocity of electron is 2 x 10 4 m s then electron mobility in m V s will be O4x 10 6 2x 10 4 10 6 4 10 4

The scale of a galvanometer is divided into 150 equal has a current sensitivity divisions The galvanometer of 15div per mA and voltage sensitivity of 3 div per millivolt What is the resistance of the galvanometer A 100 B 15 YOU C 52 C G

5 There is a glass slab of refractive index 4 face AB and emerge from face BC see figure is the angle of minimum deviation by these faces and 0 is the deviation of ray which enters the face AB along AB then B 90 sino a sin 0 20 C F 11 54 A light ray enters from is Find value of a

139 A 50 cm long bar magnet AB is moved with a speed of 4 m sec in a magnetic field B 0 01T as shown in figure The emf generated is 1 0 01 v XXXXX X X X X X X X X X X X X X X X X X X X X 2 0 02 V B 3 0 03 V 4 0 04 V

A 20 volts AC is applied to circuit consisting of a resistance and a coil with negligible resistance If the voltage across the resistance is 12 V the voltage across the coil is O 16 V O 10 V O 8 V 26x

In AC series circuit the resistance inductive reactance and capacitive reactance are 3 0 100 and 14 Q respectively The impedance of circuit is 050 40 070 10 Q

20 A magnet is suspended horizontally in the earth s magnetic field When it is displaced and then released it oscillates is a horizontal plane with a period T If a piece of wood of same moment of inertia about the axis of rotation as the magnet is attached to the magnet what would the new period of oscillation of the system become T T 3 2 T 2 1 3 2 4 2 T

23 The potential energy of a particle of mass 1 kg x 2 moving along x axis given by U x x J If total mechanical energy of particle is 2 J its maximum speed is 1 3 m s 3 1 m s 2 2 m s 4 5 m s

2 Example 2 21 Prove that ax b a b a b Sol Let a a b b and be the angle between them ax b ab sin 0 a b sin 0 a b 1 cos 0 a b ab cos 0 2 212 2 b DUIS

PLEASE SOLVE THE FOLLOWING TOPIC ELECTRIC AND MAGNECTIC FIELDS 2 3 pts Consider two points P 1 2 2 and Q 3 90 2 Find the distance just length between P and Q

A uniform stick of mass m 24 kg and length 1 1m spins around on a frictionless horizontal plane with its CM stationary A mass M is placed on the plane and the stick collides elastically with it as shown with the contact point being the end of the stick 1 What should M in kg be so that after the collision the stick has translational motion but no rotational motion

Question sir 1 Under which fundamental force should we include ele

ALLEN Topic SYLLABUS 1 A projectile is thrown with velocity u 20 m s 5 1 at an angle 60 with horizontal If the projectile comes back on the ground at the same level then which of following cannot be a possible answer for range Consider g 10 m s 1 34 6 m 2 37 5 m 60 u 20 m s 5 af an a affer 1 g 10 m s ffery 2 37 5 m 1 34 6 m

A particle of mass 6 kg is at the origin Another particle of mass 0 4 kg is at a distance of 8 m on the X axis Then the distance of centre of mass of the system from the origin is a 0 5 m b 0 2 m c 0 4 m d 0 8 m

Example 2 20 Ifax b bx c 0 with a C that a c kb where k is scalar Sol Given parallel concept onstrimusis bxc llow an A of axb cxb Sidur scalar axb cxb 0 a c b 0 RXA Given a x b 0 bx c 0 a b c d are non zero vectors a c 0 olen 00 ai 8 Hence a c is parallel to b 53 NOV a c kb where k is

17 Three boys A B and C decide to walk on straight tracks parallel to a power line in which poles are 18 m apart Boys A and B walk on the same track while C on a different track in the same direction with velocities 4 m s 2 m s and 2 m s respectively The track of boys A and B is equidistant from the power line and from the track of the boy C In the beginning all the boys and one of the poles are in a line that is perpendicular to the power line Draw a graph to show how does number of poles that the boy C can see through the space between boys A and B vary with time Track of boy A and B Track of boy C

2 Three particles start from the origin at the same 12 time one with a velocity v along the x axis second along the negative y axis with a velocity v and third particle moves along the line x y The velocity of third particle so that three may always lie on the same line is 2 V1 V V 2 V V V V 4 v V 2V1 V2 V V 1 a V V fared for at gangen fra et V1 V 2 V1 V V1 V fa fa 2 VI V 4 V 2V1 V2 V V I

Q 7 O A river flows east to west at a speed 5 m min A man capable of swimming 10 m min in still water is standing on the south bank of the river He wants to swim across the river in the shortest time possible Which of the following path should he choose O Due North 1 Due North East 00 47

In the arrangement shown AB is a fixed current carrying long wire Wire CD is held stationary with the help of an ideal string in gravity If tension in the string is two times the weight of wire CD mass per unit length of wire CD is Tey adda AB yg tida ugaidi ma ar fi yg f JA H agum CD FOR 1 uf 39 a ar CD chl y ad ar CD ufa sis IS WHA ci DT

Smooth surface A Doubt Let s say a my doubt is when we V use ball is rolling from B to A Work done by all at rut when released B mgh 1 m 1 mrz vegn Whil don t the formula Up 0 We con Change indispt in kineticey

The velocity in m s of a body moving in a straight line as a function of time in sec is given by v t 6 t 12 If the body starts from origin the magnitude of velocity when it again passes through the origin is

If A 1 2 3k and B 21 21 3k then angle between A and B is 1 cos 13 3 2 sin 3 tan 53 4 tan 1 3 af A i 2j 3k qi B 2i 2j 3k 4 3 tan 53 1 cos 2 sin

Which of the following expression correctly represents the change in root mean square velocity of a gas mol mass M if the temperature of gas changes by AT 1 3RAT Vims 2RAT 3RAT 2 2MVms 3RAT

A charged particle of charge q and mass m enters perpendicularly in a magnetic field B Kinetic energy a particle is E then time period of rotation is O O O TUM qB 2 m qB 2 m qBE

In a potentiometer experiment the balancing length of the cell was found to be 80 cm Now a resistance of 8 Q is connected across the terminal of this cell the balancing length becomes 60 cm The internal resistance of this cell is O 813 2 1 22 020

Q 3 O 1 A man travelling in a bus moves from west to east with a speed of 40 km hr He observes that the raindrops are falling vertically down To another man standing on the ground the rain will appear O 02 03 to be falling vertically down to be falling at an angle going from east to west to be falling at an angle going from west to east

In the L R circuit the value of Lis TU value of resistance Ris 30 Q If in the circuit an alternating emf of 200 V at 50 cycles sec is connected the impedance of circuit and current respectively will be O 11 4Q 17 5 A 30 7 0 6 5 A 40 4 0 5 A 0 4 50 Q 4 A H and

18 Two substances A and B of equal mass mare heater 1 A graph between temperature and time is shown i at uniform rate of 6 cal s under similar conditions HA figure Ratio of heat absorbed complete fusion is a 9 Temperature C 100 80 60 40 20 b HB 0 1 2 3 4 5 6 7 4 24 c by them for A B Time d 5

ALLEN The main scale of a Vernier calliper reads in mm 9 and its Vernier is divided into 10 divisions which coincide with 9 divisions of the main scale The reading for the situation is found to be x 10 mm Find the value of x In fig 1 8th div of V S coincides with M S D in fig 2 6th div of V S coincides with M S D Fig 1 Fig 2 1 104 2 108 3 114 4 118 em 0 10 cm 0 10 1 Lo 2 10 Consider the vernier caliners as shown 10 after fervan you turn fact after a 10 9 you fufa ferya x 10 mm fig 1 V S fig 2 Sud f Fig 1 0 Cm Fig 2 1 104 2 108 3 114 4 118 0 cm 10 B fafar faen en f ftia 1 10 after havi 2 10 3 PLE

Three forces acting on a body are shown in 2 figure To have the resultant force only along y direction the magnitude of the minimum additional force needed is 4N 1 0 5N 30 IN 2 1 5N 4 3N IA 1 2 3k and 3 3 and a f at after a a 4N 30 1 0 5N 3 N afe A 1 2j 3 km IN 2 1 5N 4 3N

12 A beam of protons with speed 4 x 10 ms enters a uniform magnetic field of 0 3 T at an angle of 60 to the magnetic field The pitch of the resulting helical path of protons is close to Mass of the proton 1 67 x 107 kg charge of the proton 1 69 x 10 C 1 12 cm 2 2 cm 3 4 cm 4 5 cm

um 2 9 A gas mixture consists of 3 moles of oxygen and 5 moles of argon at temperature T Assuming the gases to be ideal and the oxygen bond to be rigid the total internal energy in units of RT of the mixture is

24 The temperature of a room heated by a heater is 20 C when outside temperature is 20 C and it is 10 C when the outside temperature is t of the heater is 40 C The temperature 1 40 C 3 100 C 2 60 C 4 75 C

2 20 A particle of mass m with an initial velocity ui collides perfectly elastically with a mass 3m at rest It moves with a velocity vj after collision then v is given by uomo 2 v U 1 0 3 1 3 v U 16 2 v U 3 4 v

18 Shown in the figure is rigid and uniform one meter long rod AB held in horizontal position by two strings tied to its ends and attached to the ceiling The rod is of mass m and has another weight of mass 2m hung at a distance of 75 cm from A The tension in the string at A is 0 25 AL 1 0 75 mg 3 0 5 mg 50 75 2m 100 B 2 1 mg 4 2 mg

V V 4 The position vector of a particle is V V 7 a cos ot i a sin cot j The velocity of the particle is 1 parallel to position vector 2 perpendicular to position vector 3 directed towards the origin 4 directed away from the origin 13 3 4 V VI V aff after 1 ff 2 ff V V1 T a cos est i a sin est j 3 gefirgaf sine fara 4 fire fra

A cylindrical capillary tube of 0 2 mm radius is made by joining two capillaries T and T of different materials having water contact angles of 0 and 60 respectively The capillary tube is dipped vertically in water in two different configurations case I and II as shown in figure Which of the following option s is are correct Surface tension of water 0 075 N m density of water 1000 kg m take g 10 m s Case I T2 T1 Case II T1 T2 A For case II if the capillary joint is 5 cm above the water surface the height of water column raised in the tube will be 3 75 cm Neglect the weight of the water in the meniscus B For case I if the joint is kept at 8 cm above the water surface the height of water column in the tube will be 7 5 cm Neglect the weight of the water in the meniscus C For case I if the capillary joint is 5 cm above the water surface the height of water column raised in the tube will be more than 8 75 cm Neglect the weight of the water in the meniscus D The correction in the height of water column raised in the tube due to weight of

same direction as shown in figure Conductor carries a current of 150 A and is held firmly position Conductor B carries a current I and allowed to slide freely up and down parallel to A between a set of non conducting guides If the mas per unit length of conductor B is 0 100 g cm wh value of current I will result in equilibrium when th distance between the two conductors is 2 50 cm IA TH IB 250 3 1 3 25 2 2 4 125 3 12 5 OB A

Q 12 O O A ship A is moving Westwards with a speed of 10 km h and a ship B 100 km South of A is moving Northwards with a speed of 10 km h The time after which the distance between them becomes shortest is O Oh 5 h 1 5 2h 00 03

50 in the circuit shown what is the approximate current passing through the resistor R A PE Simo 075 A 0 2 C 0 84 A D 0 28 A t td G TE U R 10 2 10 V 4 D 6 V 3V 6V B S14 R 52 R 6525 u e F 6 sim 0 R 852 us 4 DEL X 12 Faqed 296 12

galvanometer The maximum current that can be passed through a of resistance 252 is 6mA It is converted into a voltmeter of range 0 to 6V by connecting a suitable resistance X to the galvanometer Identify the correct choice about X A X 575 in series X 8000 in parallel B O X YOU C X 975 in parallel D X 975 in series

of capacitance 1 F is charged 50 A capacito shown in the figure When switch S is turned to position 2 the percentage of its stored energy dissipated is of Aakas 100 1 KS 1 F 2 4 F 2 80 0 60 Vi v For th

A 5000 kg rocket is set for vertical firin g The exhaust speed is 800 m s what is the amount of gas ejected per secon d to supply the needed thrust and to giv e an upward acceleration of 20 m s the amount of gas ejected per second to apply the need thrust will be g 10 m s A 127 5 Kg s B 187 5 Kg s C 187 5 Kg s D 137 5Kg s

Consider 12 identical resistors of resistance R each are connected symmetrically in t shape of a square bi pyramid ABCDEF Which of the following options about equivalent resistance is are correct A 6 A The effective resistance between E and F is R 2 B The effective resistance between A and C is R 2 C The effective resistance between A and B is R 2 D The effective resistance between A and B is 5R 12

Q 11 O O The speed of a swimmer in still water is 20 m s The speed of river water is 10 m s and is flowing due east If he is standing on the south bank and wishes to cross the river along the shortest path the angle at which he should make his strokes w r t north is given by O 60 west 45 west 1 30 west 00 03 O