Current Electricity. Assignment For Foundation Classes Summer vacation Home work

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1 ssignment For Foundation Classes Summer vacation Home work Current Electricity. Figure shows a simple potentiometer circuit for measuring a small e.m.f. produced by a thermocouple. The meter wire PQ has a resistance 5 and the driver cell has an e.m.f. of V. If a balance point is obtained m along PQ when measuring an e.m.f. of 6.00 mv, what is the value of resistance m P Q None of these Thermocouple G 6.00 mv. car has a fresh battery of e.m.f. V and internal resistance of If the starter motor draws a current of 90, the terminal voltage when the starter is on will be V 8.5 V 0.5 V 7.5 V. If the balance point is obtained at the 5th cm in a metre bridge the resistances in the left and right gaps are in the ratio of 7 : : 7 9 : : 9 4. Find the equivalent resistance across the terminals of source of e.m.f. 4 V for the circuit shown in figure E=4V In the circuit shown in figure, switch is initially closed and is S S open. Find Va Vb b 5 4 V 0 F 8 V V 6 V a 4V S 6. The figure here shows a portion of a circuit. What are the magnitude and direction of the current i in the lower right-hand wire carbon resistor has colour strips as violet, yellow brown i and golden. The resistance is 64 0 S 74 V voltmeter of resistance 000 is connected across a resistance of 500 in the given circuit. What will be the reading of voltmeter V V 6 V 4 V 9. beam contains 08 doubly charged positive ions per cubic centimeter, all of which are moving with a speed of 05 m/s. The current density is 6.4 /m. /m.6 /m None of these 0. In the circuit shown, the reading of ammeter when switch S is open and when switch S is closed respectively are and 4 S 4 and 5 5 and 6 6 and 7. In the circuit as shown in figure the esistance = 46 Current through 0 resistance is 0. Potential difference across the middle resistance is V ll option are correct. In figure shows a rectangular block with dimensions x, x and 4x. Electrical contacts can be made to the block between opposite pairs of faces (for example, between the faces labelled -, - and C-C). etween which two faces would the maximum electrical resistance be obtained (- : Top and bottom faces, - : Left and right faces, C-C : Front and rear faces) - C-C 5V - Same for all three pairs. battery is connected to a uniform resistance wire and is earthed. Which one of the graphs below shows how the current density J varies along J C x + V 500 0V C x 4x J 0 V Zero at all points 0

2 4. cylindrical metal wire of length l and cross sections area S, has resistance, conductance G, conductivity and resistivity. Which one of the following expressions for is valid G G GS l l S 5. potential divider is used to give outputs of 4 V and 8 V from a V source. Which combination of resistances, (,, ) gives the correct voltages? : : : : : : : : : : 0 Volt 6. Find equivalent resistance between and 4 7. Following figure shows four situations in which positive and negative charges moves horizontally through a region and gives the rate at which each charge moves. ank the situations according to the effective current through the region greatest first + 7C/sec (i) J 0 i = ii = iii = iv i = ii = iii > iv C/sec + (ii) +V i > ii > iii > iv i = ii = iii < iv 8. and are two square plates of same metal and same thickness but length of is twice that of. atio of resistances of and is C/sec 4C/sec J 0 + 5C/sec (iii) +8V +4V 6C/sec + C/sec (iv) 4 : : 4 : : 9. moving coil galvanometer is converted into an ammeter reading upto 0.0 by connecting a shunt of resistance 4 r across it and into an ammeter reading upto 0.06 when a shunt of resistance r is connected across it. What is the maximum current which can be sent through this galvanometer if no shunt is used [ Two conductors are made of the same material and have the same length. Conductor is a solid wire of diameter.0 mm. Conductor is a hollow tube of outside diameter.0 mm and inside diameter.0 mm. The resistance ratio / will be 4. wire has resistance of 4 is bent in the following shape. The effective resistance between and is None of these. In the circuit shown in figure, find the current through the branch D D. battery of 4 cells, each of emf.5 V and internal resistance is to be connected in order to send the maximum current through a resistor. The correct arrangement of cells will be rows of cells connected in parallel rows of 8 cells connected in parallel 4 rows of 6 cells connected in parallel ll of these 5 V cm 6 0 cm C 0 V

3 Gravitation. Two identical spheres are placed in contact with each other. The force of gravitation between the spheres will be proportional to ( = radius of each sphere) 4 None of these. Suppose that the force of earth's gravity suddenly disappears, choose the correct answer out of the following statements The weight of the body will become zero but mass remains the same The mass of the body will become zero but the weight remains the same oth the mass and weight will be the same Mass and weight will remain the same. n earth satellite is moved from one stable circular orbit to a further stable circular orbit, which one of the following quantities increase Gravitational force Gravitational P.E. Linear orbital speed Centripetal acceleration 4. Two planets revolve round the sun with frequencies N and N revolutions per year. If their average orbital radii be and respectively, then / is equal to / / ) ( N N / / ) ( N N / / ) ( N N / / ) ( N N 5. There is no atmosphere on the moon because It is closer to the earth It revolves round the earth It gets light from the sun The escape velocity of gas molecules is lesser than their root mean square velocity here 6. Two heavenly bodies S and S, not far off from each other are seen to revolve in orbits round their common centre of mass Which are arbitrary With S fixed and S moving round S With S fixed and S moving round S 7. The mass of the moon is about.% of the mass of the earth. Compared to the gravitational force the earth exerts on the moon, the gravitational force the moon exerts on earth Is the same Is smaller Is greater Varies with its phase 8. clock S is based on oscillation of a spring and a clock P is based on pendulum motion. oth clocks run at the same rate on earth. On a planet having the same density as earth but twice the radius S will run faster than P P will run faster than S They will both run at the same rate as on the earth None of these 9. Consider earth to be a homogeneous sphere. Scientist goes deep down in a mine and scientist goes high up in a balloon. The value of g measured by goes on decreasing and that by goes on increasing goes on decreasing and that by goes on increasing Each decreases at the same rate Each decreases at different rates 0. The mass of the moon is of the earth but the gravitational pull 8 is 6 of the earth. It is due to the fact that 8 The radius of the moon is of the earth 6 The radius of the earth is 9 6 of the moon Moon is the satellite of the earth None of the above. weight is suspended from the ceiling of a lift by a spring balance. When the lift is stationary the spring balance reads W. If the lift suddenly falls freely under gravity, the reading on the spring balance will be W W W/ 0. If a planet consists of a satellite whose mass and radius were both half that of the earth, the acceleration due to gravity at its surface would be (g on earth = 9.8 m/sec ) 4.9 m / sec 9.6 m / sec 8.9 m / 9.4 m / sec sec. t a given place where acceleration due to gravity is g sphere of lead of density d m / sec, a kg / m is gently released in a column of liquid of density ' ' kg / m. If d, the sphere will Fall vertically with an acceleration g Fall vertically with no acceleration Fall vertically with an acceleration Fall vertically with an acceleration 4. g e and m / sec d g d g d g p denote the acceleration due to gravity on the surface of the earth and another planet whose mass and radius are twice as that of earth. Then g g g / p p e e p g e g g g / 4 p g e 5. If the value of g at the surface of the earth is 9.8 m / sec, then the value of g at a place 480 km above the surface of the earth will be (adius of the earth is 6400 km) 8.4 m / sec 7. m / sec 9.8 m / sec 4. m / sec 6. The acceleration due to gravity about the earth's surface would be half of its value on the surface of the earth at an altitude of ( = 4000 mile) 00 mile 600 mile 000 mile 4000 mile

4 7. pendulum clock is set to give correct time at the sea level. This clock is moved to hill station at an altitude of 500 m above the sea level. In order to keep correct time of the hill station, the length of the pendulum Has to be reduced Has to be increased Needs no adjustment Needs no adjustment but its mass has to be increased 8. t some point the gravitational potential and also the gravitational field due to earth is zero. The point is On earth's surface elow earth's surface t a height earth) t infinity e from earth's surface ( radius of the 9. body falls freely under gravity. Its speed is v when it has lost an amount U of the gravitational energy. Then its mass is Ug v U v U g Ugv 0. The ratio of the radius of the earth to that of the moon is 0. The ratio of acceleration due to gravity on the earth and on the moon is 6. The ratio of the escape velocity from the earth's surface to that from the moon is 0 6 Nearly Escape velocity from the moon surface is less than that on the earth surface, because Moon has no atmosphere while the earth has adius of moon is less than that of the earth Moon is nearer to the sun Moon is attracted by other planets. The ratio of the radius of a planet to that of planet is r. The ratio of acceleration due to gravity on the planets is x. The ratio of the escape velocities from the two planets is e xr rx. Time period of revolution of a nearest satellite around a planet of radius is T. Period of revolution around another planet, whose radius is but having same density is T T r x x r 9T T 4. The maximum possible velocity of a satellite orbiting round the earth in a stable orbit is e g e g e g Infinite 5. man inside an artificial satellite feels weightlessness because the force of attraction due to earth is Zero at that place Is balanced by the force of attraction due to moon Equal to the centripetal force Non-effective due to particular design of the satellite 6. Two identical satellites and are circulating round the earth at the height of and respectively, (where is radius of the earth). The ratio of kinetic energy of to that of is 7. The mean radius of the earth's orbit round the sun is.5 0. The mean radius of the orbit of mercury round the sun is m. The mercury will rotate around the sun in year Nearly 4 year Nearly 4 years.5 years

5 Law of Motion. car is moving with uniform velocity on a rough horizontal road. Therefore, according to Newton's first law of motion No force is being applied by its engine force is surely being applied by its engine n acceleration is being produced in the car The kinetic energy of the car is increasing. person is sitting in a travelling train and facing the engine. He tosses up a coin and the coin falls behind him. It can be concluded that the train is Moving forward and gaining speed Moving forward and losing speed Moving forward with uniform speed Moving backward with uniform speed. block can slide on a smooth inclined plane of inclination kept on the floor of a lift. When the lift is descending with a retardation a, the acceleration of the block relative to the incline is ( g a) sin ( g a) g sin ( g a) sin kg man stands on a spring scale in the lift. t some instant he finds, scale reading has changed from 60 kg to 50kg for a while and then comes back to the original mark. What should we conclude? The lift was in constant motion upwards The lift was in constant motion downwards The lift while in constant motion upwards, is stopped suddenly The lift while in constant motion downwards, is suddenly stopped 5. When a body is acted by a constant force, then which of the following quantities remains constant Velocity Momentum cceleration None of these 6. man of weight mg is moving up in a rocket with acceleration 4 g. The apparent weight of the man in the rocket is Zero 5 mg 4 mg mg 7. spring balance and a physical balance are kept in a lift. In these balances equal masses are placed. If now the lift starts moving upwards with constant acceleration, then The reading of spring balance will increase and the equilibrium position of the physical balance will disturb The reading of spring balance will remain unchanged and physical balance will remain in equilibrium The reading of spring balance will decrease and physical balance will remain in equilibrium The reading of spring balance will increase and the physical balance will remain in equilibrium 8. s shown in the figure, two equal masses each of kg are suspended from a spring balance. The reading of the spring balance will be Zero kg 4 kg kg etween zero and kg 9. player kicks a football of mass 0.5 kg and the football begins to move with a velocity of 0 m/s. If the contact between the leg and the football lasts for sec, then the force acted on the football 50 should be 500 N 50 N 50 N 65 N 5 0. The engine of a jet aircraft applies a thrust force of 0 N during take off and causes the plane to attain a velocity of km/sec in 0 sec. The mass of the plane is 0 kg 0 kg 4 0 kg 0 kg. force of 50 dynes is acted on a body of mass 5 g which is at rest for an interval of seconds, then impulse is N-s N-s.5 0 N-s.5 0 N-s. Two weights w and w are suspended from the ends of a light string passing over a smooth fixed pulley. If the pulley is pulled up at an acceleration g, the tension in the string will be 4ww w w ww w w ww w w ww ( w w ) 5 kg

6 . The masses of 0 kg and 0 kg respectively are connected by a massless spring as shown in figure. force of 00 N acts on the 0 kg mass. t the instant shown, the 0 kg mass has acceleration m / sec. What is the acceleration of 0 kg mass 0 kg 00N 0 kg m / sec 4 m / sec 0 m / sec Zero 4. Two masses M and m are connected by a weightless string. They are pulled by a force F on a frictionless horizontal surface. The tension in the string will be FM m M FM m M T m F F M m Fm M m 5. In the above question, the acceleration of mass m is F m F T m F T m 6. Three weight, and C are connected by string as shown in the figure. The system moves over a frictionless pulley. The tension in the string connecting and is (where g is acceleration due to gravity) g g 9 8 g 9 0g 9 F M kg kg C 5 kg

7 Magnetism. In the hydrogen atom, the electron is making r. p. s. If the radius of the orbit is metre, then magnetic field produced at the centre of the orbit is 40 Tesla.5 Tesla.4 Tesla 0.4 Tesla. coil carrying a heavy current and having large number of turns mounted in a N-S vertical plane and a current flows in clockwise direction. small magnetic needle at its cente will have its north pole in East-north direction West-north direction East-south direction West-south direction. charged particle is projected in a plane perpendicular to a uniform magnetic field. The area bounded by the path described by the particle is proportional to The velocity The momentum The kinetic energy None of these 4. In figure shows three long straight wires P, Q and carrying currents normal to the plane of the paper. ll three currents have the same magnitude. Which arrow best shows the direction of the resultant force on the wire P C D C D 5. moving coil galvanometer has 48 turns and area of coil is m 4 0. If the magnetic field is 0. T, then to increase the current sensitivity by 5% without changing area () and field () the number of turns should become Figure shows a straight wire of length l current i. The magnitude of magnetic field produced by the current at point P is 0 i l l P 0i i 4 l l 0 i 8 l 0i l 7. winding wire which is used to frame a solenoid can bear a maximum 0 current. If length of solenoid is 80cm and it's cross sectional radius is cm then required length of winding wire is ( 0. T). 0 m m.4 0 m 6 0 m P Q 5 8. current carrying wire LN is bent in the from shown below. If wire carries a current of 0 and it is placed in a magnetic field of 5T which acts perpendicular to the paper outwards then it will experience a force 6 cm Zero 4 cm 5 N 0 N L 0 N 9. wire of length L is bent in the form of a circular coil and current i is passed through it. If this coil is placed in a magnetic field then the torque acting on the coil will be maximum when the number of turns is s large as possible ny number 0. particle having a charge of 0.0 C and mass g moves in a circle of radius 0 cm under the influence of a magnetic field of induction 0.T. When the particle is at a point P, a uniform electric field is switched on so that the particle starts moving along the tangent with a uniform velocity. The electric field is 0. V/m.0 V/m 0.0 V/m 00 V/m. Two parallel long wires carry currents and with i i i i. When the currents are in the same direction, the magnetic field midway between the wires is 0 T. When the direction of is reversed, it i becomes 40 T. the ratio i / i is : 4 : 7 7 : 5 :. Two circular coils X and Y, having equal number of turns, carry equal currents in the same sense and subtend same solid angle at point O. If the smaller coil, X is midway between O and Y, then if we represent the magnetic induction due to bigger coil Y at O as Y and that due to smaller coil X at O as, then X Y X Y X Y X Y X 4 Y r N d 4 cm P r X d/ O

8 . fixed horizontal wire carries a current of 00. nother wire having a mass per unit length 0 kg / m is placed below the first wire at a distance of cm and parallel to it. How much current must be passed through the second wire if it floats in air without any support? What should be the direction of current in it 5 (direction of current is same to first wire) 5 (direction of current is opposite to first wire) 49 (direction of current is same to first wire) 49 (direction of current is opposite to first wire) 4. Find magnetic field at O 5 0 i 4 r 0 i 4 r Zero 0 i 4 r 5. square loop of side a hangs from an insulating hanger of spring balance. The magnetic field of strength occurs only at the lower edge. It carries a current I. Find the change in the reading of the spring balance if the direction of current is reversed Ia Ia Ia Ia 6. charge of.0 C moves with a speed of.0 0 ms along + ve X-axis magnetic field of strength 0. kˆ Tesla exists in space. What is the magnetic force ( F m ) on the charge F m. N along + ve x direction I F m. N along ve x direction F m. N along + ve y direction F m. N along ve y direction r r r Spring balance Insulating hanger i O 6 7. Five very long, straight wires are bound together to form a small cable. Currents carried by the wires are I 0, I 6, I, I4 7, I5 8. The magnetic induction at a distance of 0 cm from the cable is 4 T 74 mt 4 mt 74 T 8. Following figure shows the path of an electron that passes through two regions containing uniform magnetic fields of magnitudes and. It's path in each region is a half circle, choose the correct option is into the page and it is stronger than is in to the page and it is weaker than is out of the page and it is weaker than is out of the page and it is stronger than 9. The square loop CD, carrying a current i, is placed in uniform magnetic field, as shown. The loop can rotate about the axis XX'. The plane of the loop makes and angle ( < 90 ) with the direction of. Through what angle will the loop rotate by itself before the torque on it becomes zero cylindrical conductor of radius '' carries a current 'i'. The value of magnetic field at a point which is /4 distance inside from the surface is 0 T. Find the value of magnetic field at point which is 4 distance outside from the surface 4 8 T T T T. Three long straight wires are connected parallel to each other across a battery of negligible internal resistance. The ratio of their resistances are : 4 : 5. What is the ratio of distances of middle wire from the others if the net force experienced by it is zero 4 : : 5 : : i X X C D Z

Chapter 12. Magnetism and Electromagnetism

Chapter 12. Magnetism and Electromagnetism Chapter 12 Magnetism and Electromagnetism 167 168 AP Physics Multiple Choice Practice Magnetism and Electromagnetism SECTION A Magnetostatics 1. Four infinitely long wires are arranged as shown in the