CBSE  /  Class 10  /  Science  /  Magnetic Effects of Electric Current

  • 1. 
    Choose the incorrect statements from the following regarding magnetic lines of field.

  • the direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points
  • magnetic field lines are closed curves
  • if magnetic field lines are parallel and equidistant, they represent zero field strength
  • relative strength of magnetic field is shown by the degree of closeness of the field lines.

  • 2. 
    If the key in the arrangement figure given below is taken out (the circuit is made open) and magnetic . field lines are drawn over the horizontal plane ABCD, the lines are

  • concentric circles
  • elliptical in shape
  • straight lines parallel to each other (Due to earth’s magnetic field)
  • concentric circles near the point O but of elliptical shapes as we go away from it.

  • 3. 
    A circular loop placed in a plane perpendicular to the plane of paper carries a current when the keys is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anticlockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the faces close to

  • A
  • B
  • A if the current is small, and B if the current is large
  • B if the current is small and A if the current is large.

  • 4. 
    For a current in a long straight solenoid, N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is

  • the field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid
  • the strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil
  • the pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet
  • the N- and S-poles exchange position when the direction of current through the solenoid is reversed.

  • 5. 
    In the arrangement shown in the figure there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then

  • the deflection in the galvanometer remains zero throughout.
  • there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the keys is removed.
  • there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction.
  • there are momentary galvanometer deflections that die out shortly; the deflection are in opposite directions.

  • 6. 
    Choose the incorrect statement

  • Fleming’s right-hand rule is a simple rule to know the direction of induced current.
  • The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors.
  • The difference between the direct and alternating currents is that the current always flows in one direction, whereas the alternating current reverses its direction periodically.
  • In India, the AC changes direction after every \(\frac{1}{50}\) second.

  • 7. 
    A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of magnetic field at a point will be North to South

  • directly above the wire
  • directly below the wire
  • at a point located in the plane of the paper, on the north side of the wire
  • at a point located in the plane of the paper, on the south side of the wire.

  • 8. 
    The strength of magnetic field inside a long current carrying straight solenoid is

  • more at the ends than at the centre
  • minimum in the middle
  • same at all points
  • found to increase from one end to the other

  • 9. 
    The most important safety method used for protecting home appliances from short circuiting or overloading is by

  • earthing
  • use of fuse
  • use of stabilizers
  • use of electric meter.

  • 10. 
    Select the incorrect statement

  • Magnetic field lines are closed curves
  • No two field lines can cross each other
  • Field lines can cross each other
  • The relative strength of the magnetic field is shown by degree of closness of the field lines.
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