MCQ of Moving Charges and Magnetism | Chapter 4 | Physics | Class 12 |

MCQ of Moving Charges and Magnetism, Chapter 4, Physics

Question 1 : A negatively charged particle is placed across a current carrying wire . Is any force experienced by the charged particle?

  1. Due to the effect of electric field , the force will be experienced by the charged particle towards right .
  2. Due to the effect of electric field , the force will be experienced by the charged particle towards left .
  3. A Torque will be applied due to the effect of magnetic field .
  4. No force will be experienced by the charged particle .

Answer : C ( A torque will be applied due to the effect of magnetic field . )

Question : 2 Give the unit of magnetic field .

  1. Tesla
  2. W b m-2
  3. N C-1 -1 s
  4. All of the above

Answer : D ( All of the above )

Question 3 : Select the CGS unit of magnetic field .

  1. Gauss
  2. Tesla
  3. Weber
  4. Maxwell 

Answer A : ( Gauss )

Question 4 : which is the correct expression for the magnetic field about infinite length conductor

   A. ( μ/4π ). ( I/a )
B. ( μ/4π ). 2 ( I/a )
C. ( μ/4π ). ( I/a ). sin ( 90° )
D. ( μ/4π ). ( I/2a )

Answer : B ( ( μo/4π ). 2 ( I/a ) )

Question 5 : Consider two concentric loops , inner and outer loop having radii ‘R1’ and ‘R2’ respectively . Inner loop having current ‘I1’ ( clockwise ) and outer loop having current ‘I2’ ( anti – clockwise ) generates magnetic field as ‘B1’ and ‘B2’ respectively .
If I1 > I2 then B net =

   A. B1 – B2
   B. B1 + B2
   C. B2 – B1
   D. None of these

Answer : A ( B1 – B2 )

Question 6 : Ampere’s Circuital law is valid for

   A. Direct current
   B. Alternating Current
   C. Both A and B
   D. Electronic Current

Answer : A ( Direct Current )

Question 7 : Magnetic field around a cylindrical wire is maximum at

   A. Axis of cylinder
   B. Outside the cylinder
   C. Inside the cylinder
   D. At surface of the cylinder

Answer : D ( At surface of the cylinder )

Question 8 : When magnetic field of certain magnitude is applied to an electron at rest , then

   A. Electron will move in the same direction as that of electric field
   B. Electron will remain stationary
   C. Electron will move perpendicular to the direction of electric field
   D. Electron will move opposite to the direction of electric field.

Answer : B ( Electron remains stationary )

Question 9 : A negatively charged particle is moving in a elliptical path with a velocity V in uniform magnetic field B , If the charged particle is accelerated to double its velocity and strength of magnetic field is reduced to half , then what how the radius of loop will be affected

   A. 8 times
   B. 4 times
   C. 2  times
   D. 16 times

Answer : B ( 4 times )

Question 10 : A charged particle is moving in a region with a constant velocity . Which of the following statement is incorrect

   A. E = 0 , B ≠ 0 ( Electric field is zero but magnetic field is non –  zero )
   B. E ≠ 0 , B ≠ 0 ( Both electric field and magnetic field are non – zero ) 
   C. E ≠ 0 , B = 0 ( Electric field is non – zero but magnetic field is zero )
   D. E = 0 , B = 0 ( Both Electric field and magnetic field is zero )

Answer : C ( E ≠ 0 , B = 0 ( ( Electric field is non – zero but magnetic field is zero ) )

Question 11 : The frequency of cyclotron is given by

   A. q b / 2πm
   B. m B / 2πq
   C. 2πm / q b
   D. 2πm / q b

Answer : A ( q B / 2πm )

You may also read MCQ of Electric Charges and Fields, MCQ of Electrostatic Potential and Capacitance, MCQ of Current Electricity, MCQ of Magnetism and Matter, MCQ of Electromagnetic Induction, MCQ of Alternating Current for better understanding of the chapters.

Question 12 : Which of the following statement in relation to magnetic force is accurate ?

   A. Magnetic forces always stick to Newton’s third law
   B. Magnetic forces don’t stick to Newton’s third law
   C. Only for high current , magnetic forces follow Newton’s third law
   D. Inside low magnetic field , magnetic forces stick to Newton’s third law

Answer : B ( Magnetic forces don’t stick to Newton’s third law )

Question 13 : A circular loop of radius 10 cm having 100 turns is carrying a current of 3.2 A .The loop is placed in vertical plane and is free to rotate around a horizontal and the vertical plane coincides with diameter of the loop. A uniform magnetic field of 5 T remains such that initially the axis of the coil is in direction of the field . Under the effect of magnetic field , the coil rotates through an angle of 60° . The magnitude of torque in the final position is

   A. 25 N m
   B. 25 √3 N m
   C. 40 N m
   D. 40 √3 N m

Answer : B ( 25 √3 N m )

Question 14 : Consider two wires , carrying current flowing in parallel and anti – parallel directions , then

   A. Parallel currents repel each other anti parallel currents attract each other .
   B. Parallel currents attract each other and antiparallel currents repel each other
   C. Both currents attract each other
   D. Both currents repel each other

Answer : B ( Parallel currents attract each other and antiparallel currents repel each other )

Question 15 : Which of the following is incorrect about cyclotron ?

   A. It is a machine to whisk charged particles or ions to high energy.
   B. Cyclotron utilizes both electric and magnetic field in combination to increment the energy of              charged particles .
   C. The cyclotron sticks to the logic that the time for one revolution of an ion is independent of its            speed or radius of its orbit .
   D. The charged particles can move in cyclotron on an arbitrary path .

Answer : D ( The charged particles can move in cyclotron on an arbitrary path. )

Question 16 : A coil having 90 turns of radius 15 cm having a magnetic field of 4× 10-4 Tesla . The amount of current flowing through it is

   A. 1.06 A
   B. 2.44 A
   C. 3.44 A
   D. 4.44 A

Answer : A ( 1.06 A )

Question 17: A moving coil galvanometer can be converted into an ammeter by doing the following step

   A. By introducing a resistor of large value in series .
   B. By introducing a shunt in parallel .
   C. By introducing a resistor of small value in series .
   D. By introducing a resistor of large value in parallel .

Answer : B ( By introducing a shunt in parallel )

Question 18 : An electron is moving with a velocity of 3.2 × 107 m s-1 in a magnetic field of 5 × 10-4 Tesla which is perpendicular to it . What will be the frequency of this electron ?

   A. 1.4 × 10 5 Hz
   B. 1.4 × 10 7 Hz
   C. 1.4 × 10 6 Hz
   D. 1.4 × 10 9 Hz

Answer : B ( 1.4 × 10 7 Hz )

Question 19 : Due to the effect of current in a circular loop having two turns  a magnetic induction of 0.2 T is produced at its center . The loop is the reoriented into circular loop of four turns . If same amount of current flows in the cold then the magnetic induction at the center of the loop now is

   A. 0.2 T
   B. 0.4 T
   C. 0.6 T
   D. 0.8 T

Answer : D ( 0.8 T )

Question 20 : If an electron is moving with velocity V and produces a magnetic field , then
   A. The direction of magnetic field will be same as direction of velocity .
   B. The direction of magnetic field will be opposite to the direction of velocity .
   C. The direction of magnetic field will be perpendicular the direction of velocity .
   D. The direction of magnetic field does not depend upon the direction of velocity .

Answer : C ( The direction of magnetic field will be perpendicular the direction of velocity .)

Question 21: Pick out the condition in which no force is experienced by the charged particle placed in magnetic field

   A. If a charged particle is at rest.
   B. If a charged particle is placed parallel to the magnetic field.
   C. If a charged particle is placed antiparallel to the magnetic field.
   D. All of these

Answer : D ( All of these )

Question 22 : Is it charged particle is moving in a cyclotron then how will the radius of the path be affected if the frequency of the radio frequency field is doubled ?

   A. The radius of path will also become half of the initial radius.
   B. The radius of part will be increased four times.
   C. The radius of path will be increased 8 times.
   D. The radius of path will remain unchanged.

Answer : D ( The radius of path will remain unchanged )

Question 23 : A positively charged particle is moving in a cyclotron having an external magnetic field of 1 T . If its oscillating frequency is 11 MHz and radius is 55 cm , then its kinetic energy in MeV is

   A. 13.36
   B. 12.52
   C. 14.89
   D. 14.49

Answer : D ( 14.49 )

Question 24 : A circular loop of 10 cm radius having 20 turns , is placed in a uniform magnetic field of 0.10 T . Given that the magnetic field is normal to the plane of coil . If the loop has cross – sectional area of 10-5 m2 , current flowing in the loop is 5 A and coil is made up of Cu having free electron density about an order of 1029 m3 . Find the net magnetic force on the loop .

   A. 2.5 × 10-25
   B. 5 × 10-25
   C. 4 × 10-25
   D. 3 × 10-25

Answer : B ( 5 × 10-25 )

Question 25 : When a magnetic compass needle is placed near a straight current carrying wire , then
(i) The straight current carrying wire will lead to a noticeable deflection in the compass needle
The needle will be aligned tangential to an imaginary circle with the straight current carrying wire

  A. Both ( i ) and ( ii ) are correct
  B. Only ( ii ) is correct
  C. Only ( i ) is correct
  D. Neither ( i ) nor ( ii ) is correct .

Answer : A ( Both ( i ) and ( ii ) are correct )

Question 26 : Which of the following is incorrect statement about the Lorentz Force ?

   A. F = q [ E ( r ) + B ( r ) ] will be the force acting on a moving charge particle in the presence of                electric field E ( r ) and magnetic field B ( r ) . 
   B. This force depends on the nature of charged particle as the magnetic field due to a negative                  charge is opposite to that of A positively charged .
   C. If the velocity and the magnetic field at parallel and anti – parallel the force due to magnetic               field then the force becomes zero .
   D. The magnetic force will be maximum for a static charge .

Answer : D ( The magnetic force will be maximum for a static charge . )

Question 27 : In an inertial frame of reference if the magnetic force applied on a moving charged particle is F then what will be its value in another inertial frame of reference

   A. It does not depends on the inertial frame of reference therefore the force will remains same.
   B. The force will be changed due to the change in the amount of charge
   C. The force will be changed due to the change in velocity of charged particle .
   D. The force will be changed due to the change in field direction.

Answer : C ( The force will be changed due to the change in velocity of charged particle)

Question 28 : When a Proton enters a uniform magnetic field with uniform velocity then what will be its trajectory

   A. Helical
   B. Circular
   C. Straight line
   D. Any one of A , B and C

Answer : D ( Any one of A , B and C )

Question 29 : A circular loop carrying current I having radius R is placed in a uniform magnetic field B which is perpendicular to the loop the force on the loop will be ,

   A. 2π RIB
   B. 2π R I2 B3
   C. π R2 I B
   D. Zero

Answer : D ( zero )

Question 30 : A straight current carrying wire of length 1 m having current of 5 ampere is suspended in mid – air by a uniform horizontal magnetic field , then find the magnitude of magnetic field given that the mass of straight current carrying wire is 1.2 Kg

   A. 0.65 T
   B. 1.53 T
   C. 2.4 T
   D. 3.2 T

Answer : C ( 2.4 T )

Question 31 : An electron enters cube across one of its face and cubical box is filled with uniform electric field and the magnetic field . If the velocity of electron is V E and A positron enters via opposite face with a velocity of – V . At a instant of time which of the following is not correct ?

   A. The electric forces on both the particles will cause same acceleration in the electron and a                    positron
   B. The magnetic forces on both a particle will cause identical acceleration in the electron and                    positron
   C. Both the particles , electron and positron will gain or lose some energy at same rate .
   D. The motion of center of mass will be determined by magnetic field only.

Answer : A ( The electric forces on both the particles will cause same acceleration in the electron and a positron )

Question 32 : A toroid is having 3700 turns with its inner and Outer radius as 28 cm and 29 cm respectively . If the current in the toroid is of then a then what will be the magnetic field inside the core of toroid .

   A. 2.60 × 10 ^ – 2 T
   B. 2.60 × 10 ^ – 3 T
   C. 4.53 × 10 ^ – 2 T
   D. 2.60 × 10 ^ – 3 T

Answer : A ( 2.60 × 10  – 2 T )

Question 33 : A straight current carrying wire ‘ A ‘ of length 10 m having current of 4 A is placed parallel at a distance of 3 m with a wire ‘ B ‘ of length 12 m and having a current of 6 A in opposite direction . Find the force on a 15 cm section of wire B near its center .

   A. 2.4 × 10 -5 N ( attractive nature )
   B. 2.4 × 10 -5 N ( repulsive nature )
   C. 1.2 × 10 -5 N ( attractive nature )
   D. 1.2 × 10 -5 N ( repulsive nature )

Answer : B ( 2.4 × 105 N ( repulsive nature ) )

Question 34 : A galvanometer can be transformed into a voltmeter by doing the following step : –

   A. By introducing a resistance of very large value in series combination with the galvanometer .
   B. By introducing a resistance of very small value in parallel combination with galvanometer .
   C. By introducing a resistance of very large value in parallel combination with the galvanometer .
   D. By introducing a very small value of resistor in series combination with the galvanometer .

Answer : A ( By introducing a resistance of very large value in series combination with the galvanometer . )

Question 35 : For a sodium atom what will be the value of Gyromagnetic ratio of an electron .

   A. The Gyromagnetic ratio will depend upon the atomic number of the atom
   B. The Gyromagnetic ratio will depend on the number of shells of the atom
   C. Gyromagnetic ratio will be independent of the orbit of the atom. 
   D. Gyromagnetic ratio will have a positive value

Answer : C ( Gyromagnetic ratio will be independent of the orbit of the atom )

Question 36 : A galvanometer of resistance 50 Ohm provides a full scale deflection for a current of 0.0 5A . If the cross-sectional area of resistance wire is 3 x 10-2 that can be used to convert the galvanometer into an ammeter which can read a maximum value of 5 A current it , then calculate the length of the wire . Given that the specific resistance of wire is 5 x 10-7 ohm m.

   A. 9 m
   B. 6 m
   C. 3 m
   D. 1.5 m

Answer : C ( 3 m )

Question 37 : Which of the following is accurate value of the Bohr magneton ?

   A. 8.99 × 10-24 A m-2
   B. 9.27 × 10-24 A m-2
   C. 5.66 × 10-24 A m-2
   D. 9.27 × 10-28 A m-2

Answer : B ( 9.27 × 10-24 A m-2 )

Question 38 : A Galvanometer shows full scale deflection for a current of 4 mA . To convert the galvanometer into a voltmeter of range 0 to 18 V , then what will be the value of resistance required . Given that the resistance of a galvanometer coil is 15 ohm .

   A. To convert the galvanometer into voltmeter a resistance of 5885 Ohm is required in series                   combination .
   B. To convert the galvanometer into voltmeter a resistance of 4485 Ohm is required in series                    combination.
   C. To convert the galvanometer into voltmeter a resistance of 5885 Ohm is required in parallel                combination .
   D. To convert the galvanometer into voltmeter a resistance of 4485 Ohm is required in parallel                combination.

Answer : B ( To convert the galvanometer into voltmeter a resistance of 4485 Ohm is required in series combination. )

Question 39 : A Galvanometer shows full scale deflection for a current of 1 mA . To convert the galvanometer into a voltmeter of a range of 2.5 V , then what will be the value of resistance required . Given that the resistance of a galvanometer coil is 10 ohm .

   A. To convert the galvanometer into voltmeter a resistance of 24.9 Ohm is required .
   B. To convert the galvanometer into voltmeter a resistance of 249 Ohm is required.
   C. To convert the galvanometer into voltmeter a resistance of 2490 Ohm is required .
   D. To convert the galvanometer into voltmeter a resistance of 24900 Ohm is required .

Answer : C ( To convert the galvanometer into voltmeter a resistance of 2490 Ohm is required)

Question 40 : The torque acting on a current carrying loop which is please in uniform magnetic field does not depend on

   A. The torque not depend on the area loop
   B. The torque not depend on the value of current
   C. The torque not depend on the magnetic field of the loop.
   D. None of these

Answer : D ( None of these )

Question 41 : Find the kinetic energy in MeV of a proton if the radius of its dees is 60 cm and frequency of cyclotron oscillator is 12 MHz

   A. Kinetic energy is 5 MeV
   B. Kinetic energy is 6.5 MeV
   C. Kinetic energy is 10.6 MeV
   D. Kinetic energy is 12.6 MeV

Answer : C ( Kinetic energy is 10.6 MeV )

Question 42 : In a uniform magnetic field of 5t the coil has a magnetic moment of 25 a M2 if the if the coil rotates with an angle of 60 degree under the influence of magnetic field is

   A. 216.5 N m
   B. 108.25 N m
   C. 102.5 N m
   D. 258.1 N m

Answer : B ( 108.25 N m )

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