Page 211 - NCERT Science Class 10 English Medium

What you have learnt

n A compass needle is a small magnet. Its one end, which points towards north, is
called a north pole, and the other end, which points towards south, is called a
south pole.
n A magnetic field exists in the region surrounding a magnet, in which the force of
the magnet can be detected.

n Field lines are used to represent a magnetic field. A field line is the path along
which a hypothetical free north pole would tend to move. The direction of the
magnetic field at a point is given by the direction that a north pole placed at that
point would take. Field lines are shown closer together where the magnetic field is
greater.
n A metallic wire carrying an electric current has associated with it a magnetic field.
The field lines about the wire consist of a series of concentric circles whose direction
is given by the right-hand rule.
n The pattern of the magnetic field around a conductor due to an electric current
flowing through it depends on the shape of the conductor. The magnetic field of a
solenoid carrying a current is similar to that of a bar magnet.
n An electromagnet consists of a core of soft iron wrapped around with a coil of
insulated copper wire.
n A current-carrying conductor when placed in a magnetic field experiences a force.
If the direction of the field and that of the current are mutually perpendicular to
each other, then the force acting on the conductor will be perpendicular to both
and will be given by Fleming’s left-hand rule.
n In our houses we receive AC electric power of 220 V with a frequency of 50 Hz. One
of the wires in this supply is with red insulation, called live wire. The other one is of
black insulation, which is a neutral wire. The potential difference between the two
is 220 V. The third is the earth wire that has green insulation and this is connected
to a metallic body deep inside earth. It is used as a safety measure to ensure that
any leakage of current to a metallic body does not give any severe shock to a user.

n Fuse is the most important safety device, used for protecting the circuits due to
short-circuiting or overloading of the circuits.

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