question_answer

  (a) State the rule to determine the direction of a (i) magnetic field produced around a straight   conductor   carrying-current. (ii) force experienced by a current-carrying straight conductor placed in a magnetic field. (iii) current induced in a coil due to its rotation in magnetic field. (b) How will the 'magnetic force get affected on (i) doubling   the   magnitude   of current? (ii) reversing the direction of current flow? Or What are magnetic and non-magnetic substances? Give two examples of each. What material is used to make permanent magnet? How can electric current be used to magnetise a coil of wire?

Answer:

  (a) (i) Ampere's Right-Hand Thumb Rule If current is passing through a conductor in the direction of thumb of the right hand, then, the direction of magnetic field is given by that of curvature of fingers.                                 (1) (ii) Fleming's   Left-Hand   Rule If  the forefinger, centre finger and thumb of left hand are stretched    mutually perpendicular are forefinger points in the direction of magnetic field, centre finger points in the direction of flow of electric current, then thumb points in the direction offeree acting on the conductor.      (1) (iii) Fleming's Right-Hand Rule If the forefinger, centre finger and thumb of right hand are stretched mutually perpendicular and forefinger points in direction of magnetic field, thumb points in the direction of motion of conductor, then centre finger points in the direction of induced current.                                                               (1) (b) (i) On doubling the magnitude of the current, magnetic force gets doubled.                                                 (1) (ii) On reversing the direction of current, direction of force gets reversed.                                                            (1) Or The substances, which get attracted by a magnet are magnetic substances, e.g., iron, nickel.      The substances which are not attracted by magnet are non-magnetic substances, e.g.,  aluminium, copper.                                                                                                                                                                                                                        Permanent magnets are made of an alloy of iron, nickel and chromium (ainico). Nipermag is also used to make permanent magnets.                                                                                                                                                     (1)          Electric current passing through a coil of wire produces magnetic field in and around the coil in the similar manner as bar magnet.                                                                                                                                                                       (1)