Magnetic Field due to current Questions and Answers

Example 5 30 A bar magnet 30 cm long is placed in the magnetic meridian with its north pole pointing south The neutral point is observed at a distance of 30 cm from its one end Calculate the pole strength of the magnet Given horizontal component of earth s field 0 34 G

c 25 cm If a circular coil of radius 20 cm having 50 turns carries a current of 2A then magnetic moment of the coil is a 0 4 2 A m c 40r A m b 4n A m d 400 A m Cturns area and current through it 1 then its

A steady current I goes through a wire loop PQR having shape of a right angle triangle with PQ 3x PR 4x and QR 5x If the magnitude of the magnetic field at P due to HOI this loop is k 48 TX a 8 b 3 find the value of k c 7 AIIMS 2014 d 5

1 A infinitely long hollow conducting cylinder with inner radius R 2 and outer radius R carries a uniform current density along its length The magnitude of magnetic field B as a function of the radial distance r from the axis is best represented by IRI R 2 1 R 2 R R 2 non moitenib 4 B IB R 2 R Y

A short bar magnet of magnetic moment 1 5 A m is placed along x axis at origin If the magnetic field along line joining origin to point P 2 3 2 0 m is T then n should be 1 3 3 9 nx10 128 2 27 4 16

Q4 A proton moves through a 0 036T magnetic field If the proton moves in a circular path with radius of 0 20m What is the speed d Ans 6 9x105 m s V 2 XB X X X x Path of charged particle

38 A current carrying closed loop in the form of a right angle isosceles triangle ABC is placed in a A B C uniform magnetic field acting along AB If the magnetic force on the arm BC is F the force on the arm AC is a 2 F c F b F d 2 F ICBSE Pre 2011

3 1m long wire is folded in form of a circular coil and 100 mA electric current is flowing in it then magnetic field at a point 1m away from its centre on its axis 1 10 5 4T 10 2T T T 2 4 10 8 2 T 8 T 41 10

0 35 SINGLE CHOICE The endpoints of a conducting string shaped as a circular loop of constant length are being pulled at a constant velocity v as shown in the figure There exists a uniform magnetic field B in space which is perpendicular to the circular loop If the loop always remains circular during the motion of its endpoints then the emf induced in the loop at t TR is 2v B R 2BRv BRU Correct Answer

Example 6 3 A long straight wire carrying current I and a square conducting wire loop of side 1 at a distance a from current wire as shown in the figure Both the current wire and loop are in the plane of paper Find the magnetic flux of current wire passing through the loop 00 a x dx

An electron gun is placed inside a long solenoid of radius R on its axis The solenoid has a turns length and caries a current I The electron gun shoots an electron along the radius of the solenoid with speed v If the electron does not hit the surface of the solenoid maximum possible value of v is all symbols have their standard meaning Z Ly 1 euonIR R Offletto euonIR 2m 3 euonIR m 2euonIR m

A circular coil of N turns and diameter d carries a current I It is unwound and rewound make another coil of diameter 2d current I remaining the same Calculate the ratio of magnetic moments of the new coil and the original coil AI 20

The area of cross section of three magnets of same length are A 2A and 6A respectively The ratio of their magnetic moments will be NIE 1 6 2 1 21 2 6 3 2 6 1 1 1 1 ME

ELECTROMAGNETIC INDUCTION K Current i flows through a long wire A square loop made of conducting wire held below the wire in the same vertical plane is released and allowed to fall under gravity If acceleration of the loop is a then 1 A current is induced in anticlockwise direction and ag 2 A current is induced in the clockwise direction and a g 3 A current is induced in anticlockwise direction and a g As shown conductin when the I flows i current 1 for a lom I flows seen by 1 R 2 B

1 A current i is flowing in a hexagonal coil of side I figure The magnetic induction at the centre of the coil will be 3 TT1 2 2 Ho OUS boolg zi H 3 3

When plane of dip circle is rotated by 90 from magnetic meridian gradually then dip shown by it 1 Increases 2 Decreases 3 First increases then decreases 4 First decreases then increases

If N pole of bar magnet is towards Earth s geographical south pole Then number of neutral points in space is 1 One 2 Two

Jorce on charge or current AU shaped wire of mass m and length is immersed with its two ends in mercury see figure The wire is in a homogeneous field of magnetic induction B If a charge that is a current pulse q idt is sent through the wire the wire will jump up The amount of charge the wire reaches a hight h is N 15 C assuming that the time of the current pulse is very small in comparison with the time of flight Make use of the fact that impulse of force equals Fdt Wb m m 10gm 20cm h 3 meters Then which equals mv B 0 1 find the value of N A long horizontal wire AR which in

21 What are the ends of a magnet called O equators O fields ples sides

20 How is magnetic force defined O The force due to the alignment of atoms The force due to motion of electric charges O The force due to the mass of an object O The force due to the pull of the Earth on an object

29 A current carrying wire carries a current of 0 63 A What is the magnitude of the magnetic field at point P 0 025 meters away from the wire 5 04 x 105 T 7 93 x 109 T O 7 93 x 108 T 5 04 x 106 T

5 A current carrying wire 0 50 m long is positioned perpendicular to a uniform magnetic field of 0 60 T If the current is 0 1 A what is the magnetic force on the wire x 0 03 N 11 1 N 33 3 N 30N

11 A wire is placed perpendicular to a uniform magnetic field of 4 6x10 T A magnetic force of 2 9x10 N is exerted on the wire If the current in the wire is 10 0 A how long is the wire 0 63 m

12 A 14 32 A current moves through a 15 0 cm wire If a magnetic force of 6 62 x104 N acts on the wire what is the magnetic field at right angles to the wire 3 08x104 T

13 A printer is connected to a 1 0 m cable If the magnetic force is 9 1x10 5 N and the magnetic field is 1 3x104 T how much current passes through the wire 0 7 A

The measures of magnetic fields B in air at points 5 cm and 25 cm away from a l straight wire carrying a current 15 A will be 5 5 x 10 11 T 1 7 10 14 T 6 0 x 10 5 T 1 2 10 5 T 5 6 10 14 T 1 5 10 9 T O 5 3x 10 4 T 1 5x 10 4 T

4 An proton traveling south through a magnetic field directed West will experience a force in what direction 5 An electron traveling south through a magnetic field directed out of the earth will experience a force

As shown in the figure two long straight wires are separated by a distance of d 0 80 m The currents are I1 2 0 A to the right in the upper wire and l2 8 0 A to the left in the lower wire What are the magnitude and direction of the magnetic field at point P which is a distance d 2 0 40 m below the lower wire u0 4 x 10 7T m A d 1

18 A nucleus of 12 protons moves at a velocity of 4 9 x 106 m s and has a magnetic force of 7 5 x 10 18 N west exerted on it If the magnetic field points upward what is the magnitude of the magnetic field 7 5x168 Which way direction was the nucleus moving 7 97 x 10 7 T

h I a 12 F2 b OF 3 F because 12 31 B 12 In the above figure if l 2 A and 12 6 A which of the following should be applicable a F 3F2 b F1 F2 c F1 F2 3 O F F O F and F are not correlated because 1 and 12 are different O3F F2 because I 1 3 12 d F1 F2

A 40 loop circular coil has a radius of 10 0 cm It is placed in a magnetic field so that th field lines from a parmanent magnet B are normal to the area of the coll If the magne is brought toward the loop so its magnetic field varies from 0 2 T to 0 70 T in 2 microsecond the induced emf through each coil would be 3 95 x 105 V O2 80 MV 1p O 87 9 x 104 V O 7 85 kV

0 Question 13 A series RL circuit formed of a R 1 20 2 resistor a L 11 0 H inductor and connected to a V 7 00 V battery a What is the time constant for this circuit b Once the switch is closed how long t does it take the current to reach half its maximum value Imax 2 O 13 1 s 5 9 s O2 9 s 8 33 s O9 2 s 6 38 s 1 pts 11 2 s 7 9 s

A solenoid consists of 180 turns of wire wound on a narrow cardboard tube like the one left after you finish a paper towel roll 19 cm long The current in the wire is 5 0 A What is the strength of the magnetic field within the tube 35 mT 1 6 T O 2 5 mT 6 0 mT

A coil of 50 loops is pulled in 0 02 s from between the poles of a magnet where its area intercepts a flux of 3 1 x 10 4 Wb to a place where the intercepted flux is 0 1 x 10 4 Wb Determine the induced emf O 7 5 V O 75 mV 0 75 V O 7 5 mV

A copper bar 30 cm long is perpendicular to a magnetic field B 0 80 Wb m2 The bar moves at right angles to the field with a speed of 0 50 m s Determine the emf induced in the bar 1 33 mV 0 12 V 2 9 V 1 pts 0 75 V

Magnetic field due to current at wire A FAV O 70 mN away from 1 Wire A with current IA O 150 N toward 1 48 N toward 1 O 15 N along I2 Bo K Wire B with current is Fo a Magnetic field due to current at wire B Two parallel cables are set apart by a distance r 10 cm Currents 1 6 0 A and A flow through the cables Find the approximate force on a 1 0 m length of cable currents are parallel take the conventional direction of current BA Exam Fear

1 A uniform magnetic field B 1 7 x 104 T exists in x direction A proton q e anc 1 67 x 10 31 kg is shot through the field in the y direction with a speed of 4 0 x 1 m s Find the magnitude and direction of the force Fg on the proton O FB 2 6 x 10 13 N toward us away from the plane of the screen O FB 3 9 x 10 11 N in x direction O FB 1 7 x 108 N in y direction O FB 1 09 x 10 16 N away from us towards the plane of the screen

Question 3 Let s take the Earth s magnetic field Be 1 80 x 104T pointing north A metal cable attached to a space station stretches radially outward by 1 8 km What would be the potential difference AV that develops between the ends of the cable if it s traveling eastward around Earth at 4 4 km s O 145 V 3 92 kV O 1 25 kV 1 pts O 1 43 kV

Question 2 1 pts What would be the magnitude and direction of force Fg on an electron q e me 9 1 x 10 31 kg shot in the y direction with a speed of 4 7 x 106 m s in a uniform magnetic field B 2 6 x 10 4 T along y direction O FB 1 95 x 10 16 N toward us away from the plane of the screen O FB 2 4 x 10 16 N away from us towards the plane of the screen O FB 0 00 N so will maintain its velocity O FB 4 9 x 10 11 N away from us towards the plane of the screen

Question 17 You have a square loop with each side of length a and a circular loop with radius a Both of these loops lie in the x y plane where there is a uniform magnetic field B pointing at some angle with respect to the positive z direction Each loop has the sa number of coils and carries the same current in the same direction Therefore the rat of magnetic moments u in the loops square circular O 4 4 1 4 T

An air core solenoid with 1100 loops is 70 cm long and has a diameter of 4 0 c current I 5 0 A flows through it what will be the approximate magnetic field generated near its axis O 30 0 mT O 10 0 mT O 40 0 mT 0 20 0 mT

You have two coils one circular with diameter of length a and another squa side of length a placed in the x y plane there is a uniform magnetic field B along the positive z direction Each loop has the same number of turns carri current in the same direction Therefore the ratio of magnetic moment u a circular square O 1 T O 4T O 4 04 T

A proton enters a magnetic field of flux density 2 5 Wb m with a velocity of 1 6 x 107 m s at an angle 30 with the field Compute the force as a vector on the proton FB 2 9 x 108 N in the plane of B O FB 6 4 x 10 16 N away from us towards the plane of the screen O FB 3 2 x 10 12 N in a direction perpendicular to B and v O FB 7 1 x 10 6 N in the x direction

A magnetic field has been set in the plane of the screen of magnitude 0 8 T due to the horse shoe magnet The wire AB shown carries a current 15 A assume the traditional direction of current as shown in the figure toward us away from the plane of screen Find the magnitude and direction of the magnetic force FB on a 5 0 cm length of the wire 2 0 N upward O 0 6 N to left O 0 4 N upward O 0 6 N from N to S of the magnets

A coil has an inductance of 1 5 H and a resistance of 0 6 ohm If the coil is suddenly connected across a 12 V battery what will be the final current O20 0 A O 20 0 mA O 120 0 A O 50 0 A

A cathode ray beam an electron beam q e m 9 1 x 10 31 kg is bent in a circle of radius 2 0 cm by a uniform field B 4 5 x 10 3 T What should be the speed of the electron as it encounters the field B O 0 6 x 1014 km s None of the speeds are correct O 1 6 x 104 km s O 1 6 x 1013 km s

6 What is the size of the current in a 35 m long wire that is perpendicular to a magnetic field of 0 085 T if the force on the wire is 125 N Round to the tenths place

ANSWER 6 A wire having a mass per unit length of 1 50 kg m carries a 3 00 A current horizontally to the north as shown In the figure What is the direction of the minimum magnetic field needed to lift this wire vertically upward ANSWER

Consider the figure below a permanent magnet is moved away from a solenoid coil Which of the following statements is correct regarding the polarity of the solenoid at point X and direction of current at point Y X is magnetic south and the current flows to the left at point Y OX is magnetic north and the current flows to the right at point Y X is magnetic south and the current flows to the right at point Y X is magnetic north and the current flows to the left at point Y No magnetic field or current are induced in this scenario

0 600 m P O zero You have a right triangular coil with base of 0 800 m and height 0 600 m having two loops and carrying a current of 2 00 A Find the magnitude of torque 7 on the coil when placed in the magnetic field B 0 500 T pointing upward in the plane of the screen paper and also in the plane of the coil O 0 96 Nm 0 48 Nm 0 800 m O 0 29 Nm R