10th Class Science Magnetic Effects of Electric Current Question Bank

done Magnetic Effects of Electric Current Total Questions - 40

• question_answer1)
  If the index finger points towards the north and the middle finger towards the east while using Fleming's left-hand rule, what will be the direction of the force acting on the conductor?
  A)
  South                                   done clear
  B)
  West done clear
  C)
  Upward                               done clear
  D)
  Downward done clear
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• question_answer2)
  What is the most appropriate reason for the popularity of AC over DC?
  A)
  AC is not continuous. done clear
  B)
  DC cannot be generated. done clear
  C)
  There is very little loss of energy in AC transmission. done clear
  D)
  There is very little gain of energy in AC transmission. done clear
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• question_answer3)
  A current that always flows in the same direction through an electrical device is called
  A)
  a direct current. done clear
  B)
  an alternating current. done clear
  C)
  a varying current. done clear
  D)
  a magnetic current. done clear
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• question_answer4)
  The direction of magnetic field at any point can be found by using
  A)
  a current carrying wire. done clear
  B)
  a compass needle. done clear
  C)
  a scale and a ruler. done clear
  D)
  a bar magnet. done clear
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• question_answer5)
  When a small magnetic needle is placed below a horizontal conductor carrying a strong current from west to east, its north pole will point in the direction of
  A)
  west - east. done clear
  B)
  south - west. done clear
  C)
  north - south. done clear
  D)
  east - west. done clear
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• question_answer6)
  A commutator changes the direction of current in the coil of
  A)
  a DC motor. done clear
  B)
  a DC motor and an AC generator. done clear
  C)
  a DC generator. done clear
  D)
  an AC generator. done clear
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• question_answer7)
  Fleming's left hand rule is used in finding the direction of the magnetic field around a
  A)
  circular loop. done clear
  B)
  moving coil. done clear
  C)
  straight conductor. done clear
  D)
  magnetic loop. done clear
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• question_answer8)
  A current carrying wire in a magnetic field results in
  A)
  an electric force. done clear
  B)
  magnetic induction. done clear
  C)
  a motor effect. done clear
  D)
  None of the above done clear
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• question_answer9)
  A magnet is inserted into the centre of a coil and an e.m.f. is induced across the coil. The magnitude of the induced current depends on
  A)
  the diameter of the coil. done clear
  B)
  the strength of a magnet. done clear
  C)
  the thickness of the wire with which the coil is made. done clear
  D)
  All of the above. done clear
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• question_answer10)
  In a circular coil, the current is found to be flowing in anticlockwise direction. In which direction is the magnetic field produced at a point on the axis of the coil?
  A)
  It is parallel to the plane of the coil. done clear
  B)
  It is perpendicular to the plane of the coil. done clear
  C)
  It is above the plane of the coil. done clear
  D)
  It is below the plane of the coil. done clear
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• question_answer11)
  What is wrong with the D.C. motor connections shown in the figure?
  A)
  Supply voltage is not correct. done clear
  B)
  Polarity of the magnets is wrong. done clear
  C)
  Polarity of the carbon brushes \[{{B}_{1}}\] and \[{{B}_{2}}\], is not correct. done clear
  D)
  Nothing is wrong with it. done clear
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• question_answer12)
  What happens when a coil carrying electric current is placed in a uniform magnetic field?
  A)
  Torque is produced done clear
  B)
  An e.m.f. is induced. done clear
  C)
  Torque is not produced. done clear
  D)
  Both (a) and (b) done clear
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• question_answer13)
  Which component in a D.C. motor reverses the flow of current in a coil?
  A)
  A battery done clear
  B)
  Carbon brushes done clear
  C)
  A commutator done clear
  D)
  A permanent magnet done clear
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• question_answer14)
  A light bar magnet is suspended near a current carrying wire as shown below. What will happen to the light bar magnet?
  A)
  It will rotate in clockwise direction. done clear
  B)
  It will rotate in anti-clockwise direction. done clear
  C)
  It will move to the right side. done clear
  D)
  It will move to the left side. done clear
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• question_answer15)
  The figure given below shows the pattern of a magnetic field formed when current flows through a conductor. Which of the following can form the pattern of the given magnetic field?
  A)
  A solenoid          done clear
  B)
  A straight wire  done clear
  C)
  A coil                                    done clear
  D)
  A bar magnet done clear
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• question_answer16)
  Two current-carrying wires (P and Q) are placed between two magnets and their currents are equal but in opposite directions as shown below. What is the direction of the force acting on each wire?
  A)

  Force on P	Force on Q
  upwards	upwards

  done clear
  B)
    

  Force on P	Force on Q
  downwards	downwards

  done clear
  C)
     

  Force on P	Force on Q
  upwards	downwards

  done clear
  D)
      

  Force on P	Force on Q
  downwards	upwards

  done clear
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• question_answer17)
  Which of the following factors affect the speed of the rotation of a direct current electric motor?
  A)
  The type of current done clear
  B)
  The direction of current done clear
  C)
  The magnitude of current done clear
  D)
  The frequency of current done clear
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• question_answer18)
  Which of the field patterns given below is valid for both electric and magnetic fields?
  A)
                              done clear
  B)
                done clear
  C)
                               done clear
  D)
  done clear
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• question_answer19)
  What is the use of split-ring commutator in a D.C. motor?
  A)
  To ensure good contact between the stationary components and the moving components done clear
  B)
  To allow the coil to rotate continuously done clear
  C)
  To ensure the unidirectional flow & current.                           done clear
  D)
  To prevent the wires from getting entangled. done clear
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• question_answer20)
  A soft iron bar is introduced inside a current carrying solenoid. What happens to its magnetic field?
  A)
  It will become zero. done clear
  B)
  It will decrease. done clear
  C)
  It will increase.                         done clear
  D)
  It will remain the same.             done clear
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• question_answer21)
  What is the purpose of carbon brushes in a D.C. motor?
  A)
  To ensure good contact between the stationary components and the moving components. done clear
  B)
  To allow the coil to rotate continuously. done clear
  C)
  To ensure the current flowing through the coil is direct current. done clear
  D)
  To prevent the wires from getting entangled. done clear
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• question_answer22)
  A straight conductor carries a current vertically upwards. Points P and Q respectively lie to the east and west of the conductor at the same distance as shown below. How is P related to Q?
  A)
  P has more magnitude than Q. done clear
  B)
  Q has more magnitude than P. done clear
  C)
  P and Q have the same magnitude. done clear
  D)
  P and Q may have the same or more magnitude. done clear
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• question_answer23)
  A current carrying conductor experiences a maximum force in a magnetic field when it is placed
  A)
  parallel to the field. done clear
  B)
  perpendicular to the field. done clear
  C)
  at an angle of \[\text{45}{}^\circ \] to the field. done clear
  D)
  at an angle of \[\text{6}0{}^\circ \] to the field. done clear
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• question_answer24)
  Which of the following does NOT increase the power of a D.C. motor?
  A)
  An increase in the number of turns in the coil done clear
  B)
  An increase in the area of cross- section of the coil done clear
  C)
  An increase in the size of the core done clear
  D)
  The winding of a large number of coils on the soft iron core done clear
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• question_answer25)
  Which of the following statements is true of Faraday's laws of electromagnetic induction?
  A)
  Whenever magnetic flux linked with a circuit changes, induced e.m.f is produced. done clear
  B)
  The induced e.m.f lasts as long as the change in the magnetic flux continues. done clear
  C)
  The magnitude of the induced e.m.f is directly proportional to the rate of change of the magnetic flux linked with the circuit. done clear
  D)
  All of the above done clear
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• question_answer26)
  Which law states that the direction of the induced current is such that it always opposes the cause (motion of conductor) which produced it?
  A)
  Ampere's law  done clear
  B)
  Ohm's law          done clear
  C)
  Lenz's law                           done clear
  D)
  Faraday's law done clear
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• question_answer27)
  Which of the following increases the turning speed of a simple D.C. motor?

  (i) An increase in the number of turns of the coil

  (ii) An increase in the input of D.C. voltage

  (iii) The inserting of a copper core in the coil

  A)
  Only (i) and (ii) done clear
  B)
  Only (i) and (iii) done clear
  C)
  Only (ii) and (iii)               done clear
  D)
  (i), (ii) and (iii)   done clear
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• question_answer28)
  Which of the following alters the direction of the current in the coil every half rotation in a D.C. motor?
  A)
  A core                                  done clear
  B)
  A commutator                  done clear
  C)
  Magnets                             done clear
  D)
  All of the above               done clear
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• question_answer29)
  Lenz's law is derived from the law of conservation of
  A)
  momentum.     done clear
  B)
  energy.                               done clear
  C)
  charge.                                done clear
  D)
  magnetism. done clear
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• question_answer30)
  On which of the following factors does the direction of the force on a current- carrying wire depend?
  A)
  On the direction of the current but not on the direction of the magnetic field done clear
  B)
  On the direction of the magnetic field but not on the direction of the current done clear
  C)
  On the direction of the current as well as the direction of the magnetic field done clear
  D)
  Neither on the direction of the current nor on the direction of the magnetic field done clear
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• question_answer31)
  What happens when two compass needles are placed near a current carrying wire at points P and Q as shown below?
  A)
  Both the needles will not deflect. done clear
  B)
  Only needle P will deflect. done clear
  C)
  Both the needles will deflect in the same direction. done clear
  D)
  Both the needles will deflect in the opposite direction. done clear
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• question_answer32)
  Which of the following does NOT use the principle of the turning effect on a coil carrying current in a magnetic field?
  A)
  Galvanometer done clear
  B)
  D.C. motor                         done clear
  C)
  A.C. motor         done clear
  D)
  D.C. generator done clear
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• question_answer33)
  The figure given below shows a current- carrying conductor placed between two magnets. Which of the given arrows correctly indicates the direction of the force acting on the conductor?
  A)
  P                                            done clear
  B)
  Q                            done clear
  C)
  R                                            done clear
  D)
  S done clear
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• question_answer34)
  The diagram given below shows a simple D.C. motor. How can the direction of the rotation be reversed?                

  	Direction of magnetic field	Direction of current
  (i)	Maintain	Reverse
  (ii)	Reverse	Maintain
  (iii)	Reverse	Reverse

  A)
  Only (i)                                done clear
  B)
  Only (ii)                               done clear
  C)
  Only (iii)                              done clear
  D)
  Only (i) and (ii) done clear
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• question_answer35)
  The difference between an A.C.  and a D.C. generator is
  A)
  an A.C. generator has commutator and a D.C. generator has slip rings. done clear
  B)
  an A.C. generator has slip rings and a D.C. generator has commutator. done clear
  C)
  A.C. generator rotates only in one direction. done clear
  D)
  the polarity of the current changes for every half rotation in a D.C. generator. done clear
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• question_answer36)
  A permanent magnet approaches a solenoid with a constant speed v .What is the magnetic pole induced at the portion Y of the solenoid and the direction of the induced current into the galvanometer?
  A)

  Polarity at Y	Direction of the current
  N-pole	From the left

  done clear
  B)

  Polarity at Y	Direction of the current
  N-pole	From the right

  done clear
  C)
   

  Polarity at Y	Direction of the current
  S-pole	From the left

  done clear
  D)
   

  Polarity at Y	Direction of the current
  S-pole	From the right

                  done clear
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• question_answer37)
  A steady current flows out of the plane of the paper in a long vertical wire. Which figure shows the direction and pattern of the magnetic field around the wire?
  A)
                             done clear
  B)
             done clear
  C)
              done clear
  D)
  done clear
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• question_answer38)
  What is the use of slip rings in a simple A.C. generator?
  A)
  To increase the rotational speed of the coil done clear
  B)
  To prevent the wire from getting entangled done clear
  C)
  To change the direction of current flowing to the load in every half a turn done clear
  D)
  To ensure good contact between the moving parts and the stationary parts done clear
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• question_answer39)
  Which of the following are the possible ways to increase the induced e.m.f. produced by a simple A.C. generator?

  (i) Increasing the rotating speed of the coils

  (ii) Placing a soft iron core in the coil

  (iii) Replacing the permanent magnets with another pair of magnets having stronger magnetic field strength

  A)
  Only (i) and (ii) done clear
  B)
  Only (ii) and (iii)               done clear
  C)
  Only (i) and (iii)                done clear
  D)
  (i), (ii) and (iii) done clear
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• question_answer40)
  Varun sprinkled iron filings on the cardboard around a current carrying wire p and then tapped the cardboard. What did he observe?
  A)

  Magnetic field	Direction
  Circular	Clockwise

  done clear
  B)
                        

  Magnetic field	Direction
  Elliptical	Anticlockwise

  done clear
  C)
                        

  Magnetic field	Direction
  Circular	Anticlockwise

  done clear
  D)
                        

  Magnetic field	Direction
  Elliptical	Clockwise

  done clear
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