Magnetic Lines of Force

Q. 1     Define Electromagnet.

Ans.     When a coil of insulated copper wire is wound around a soft iron rod & an electric current is passed through the wire, the iron rod develops magnetism & is called electromagnet.

Q. 2. Name any four devices or appliances in which electromagnetism plays an important role.

Ans.   Appliances in which electromagnetism plays an important role : Electric door bell (ding dong), speaker, electric water pump, electric generator, radios, television antenna etc.

Q.3.     Define magnetic lines of force.

Ans.  The path along which the unit north pole moves in a magnetic field is called magnetic lines of force or magnetic field lines.

Q.4 State the characteristics of magnetic lines of force.

Ans. i) Magnetic lines of force are closed, continuous curves starting from the north pole & ending at the south pole of the magnet.

ii)    The tangent at any point on the magnetic lines of force gives the direction of the magnetic field at that point.

iii)     No two magnetic lines of force can intersect each other.

iv)     Magnetic lines of force are crowded where the magnetic field is strong & far from each other where the field is weak.

Q.5 Define magnetic field.

Ans.   The region around a magnet in which the force of attraction & repulsion exist is called magnetic field Or current carrying conductor is called magnetic field.

Q.6      State any two characteristics of magnetic field.

Ans. i) As we more away from a magnet or a current carrying conductor, its magnetic field goes on decreasing.

ii)         Like gravitational field & electric field, magnetic field extends to infinity.

Q.7      What is a compass needle ?

Ans.     A compass needle is a small magnetic needle with pointed ends & behaves like a bar magnet. When suspended or pivoted (supported) freely in the earth’s magnetic field, its ends point approximately towards the geographic north & south directions are called as north pole & south pole respectively.

Q.8      State the conclusions that can be drawn from Oersted experiment.

Ans.     Conclusions that can be drawn from Oersted’s experiment are:

i)       An electric current produces a magnetic field around it. The moving charge in the conducting wire is a source of magnetic field.

ii)     The direction of the magnetic field produced by the current is the direction in which the north pole of the magnetic needle is deflected. Have from the experimental observations we conclude that any point near the current carrying conductor, the magnetic field is perpendicular to, 1) length of the conductor & 2) The line joining the conductor & the given point.

Q.9   Give scientific reasons: A magnetic crane is used to load & transport scrap iron.

Ans. I)  It is difficult to manually load & transport heavy scrap iron.

ii)     Therefore, a permanent magnet of a very big size is necessary & this cannot be easily created.

iii)      Hence, we create a powerful electromagnet by passing a current through a big iron disc.

iv)    Thus, the big disc becomes powerful magnet & the scrap iron gets attracted to it, which can be easily loaded & transported. Hence a magnetic crane is used to load & transport scrap iron.

magnetic field due to the coil,magnetic lines of flux current carrying conductor,factor on which tge strength of a magnetic field at a point due to ,current carrying cunductor depends,state 4 magnetic lines of force, magnetic field, magnetic current, the factors on which the magnetic field due to the current carrying in the circular loop depends, magnetic coil, current conductor, Right hand thumb rule, Left hand thumb rule, solenoid, magnetic lines of force, magnetic field lines, due to a current carrying solenoid,  Bar magnet, Electromagnet, magnets