Question

Explain all the points and concepts in class 10 magnetic effects of electric current.

Answer 1

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 Magnet: (i) is an object that attracts objects made of iron, cobalt & nickel.
(ii) Comes to rest in North-South direction, when suspended freely.
 Magnets are used: (i) In radio & stereo speakers, (ii) In refrigerator doors, (iii) on audio &
video cassettes players, (iv) On hard discs & floppies of computers & (v) in children‘s toys.
 Magnetic field: The area around a magnet where a magnetic force is experienced is called a
magnetic field. It is a quantity that has both direction & magnitude.
 Magnetic field lines: Magnetic field is represented by field lines. They are lines drawn in a
Magnetic field along which a North magnetic pole moves. Magnetic field lines are called as
Magnetic lines of force.
Refer to figure 13.3 & 13.4 page no. 225 of N.C.E.R.T Text book)
 Properties of Magnetic field lines:
(i) They do not intersect each other.
(ii) It is taken by convention that magnetic field lines emerge from
North pole and merge at the South pole. Inside the magnet, their
direction is from South pole to North pole. Therefore magnetic field
lines are closed curves.
 Magnetic field lines due to a current through a straight conductor (wire)- consist of series of
concentric circles whose direction is given by the Right hand thumb rule.
 Right hand thumb rule: If a current carrying straight conductor is held in your right hand such
that the thumb points towards the direction of current, then the wrapped fingers show the
direction of magnetic field lines.
(Refer to figure 13.7, page no. 228 of N.C.E.R.T Text book)
 Magnetic field lines due to a current through a circular loop
(Refer to figure 13.8, page no. 228 of N.C.E.R.T Text book)
 The strength of the magnetic field at he centre of the loop(coil)depends on:
(i) The radius of the coil- The strength of the magnetic field is inversely
proportional to the radius of the coil. If the radius increases, the
magnetic strength at the centre decreases.
(ii) The number of turns in the coil: As the number of turns in the coil
increase, the magnetic strength at the centre increases, because the
current in each circular turn is having the same direction, thus the
field due to each turn adds up.
(iii) The strength of the current flowing in the coil: as the strength of the
current increases, the strength of thee magnetic fields also increases.
 Solenoid: (Refer to figure 13.10, page no. 229 of N.C.E.R.T Text book)
 (i) A coil of many turns of insulated copper wire wrapped in the shape of a cylinder is called
a Solenoid.
(ii) Magnetic field produced by a Solenoid is similar to a bar magnet.
(iii) The strength of magnetic field is proportional to the number of turns & magnitude of
current.
13. MAGNETIC EFFECTS OF ELECTRIC CURRENT