Page 207 - NCERT Science Class 10 English Medium

3. Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.

(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.

1 1 1
12.3 .3 .32 3 .3 FORCE ON A CURRENTFORCE ON A CURRENT--C CARRYING CONDUCTORARRYING CONDUCTOR
FORCE ON A CURRENT-CARRYING CONDUCTORARRYING CONDUCTOR
ON
A
FORCE ON A CURRENT-C
CURRENT-CARRYING CONDUCTOR
12 2. 2
FORCE
IN A MAGNETIC FIELD
IN IN A A MAGNETIC FIELD
IN IN A MAGNETIC FIELDA MAGNETIC FIELD
FIELD
MAGNETIC
We have learnt that an electric current flowing through a conductor
produces a magnetic field. The field so produced exerts a force on a
magnet placed in the vicinity of the conductor. French scientist Andre
Marie Ampere (1775–1836) suggested that the magnet must also exert
an equal and opposite force on the current-carrying conductor. The force
due to a magnetic field acting on a current-carrying conductor can be
demonstrated through the following activity.
12.7
Activity 12.7
Activity 12.712.7
Activity
Activity 12.7
Activity
n Take a small aluminium rod AB (of about 5 cm). Using
two connecting wires suspend it horizontally from a
stand, as shown in Fig. 12.12.
n Place a strong horse-shoe magnet in such a way that
the rod lies between the two poles with the magnetic
field directed upwards. For this put the north pole of
the magnet vertically below and south pole vertically
above the aluminium rod (Fig. 12.12).
n Connect the aluminium rod in series with a battery,
a key and a rheostat.
n Now pass a current through the aluminium rod from
end B to end A.
n What do you observe? It is observed that the rod is
displaced towards the left. You will notice that the rod
gets displaced.
n Reverse the direction of current flowing through the Figure 12.12
Figure
Figure 12.12
Figure 12.1212.12
12.12
Figure
rod and observe the direction of its displacement. It is A current-carrying rod, AB, experiences
now towards the right. a force perpendicular to its length and
Why does the rod get displaced? the magnetic field. Support for the
magnet is not shown here, for simplicity.
The displacement of the rod in the above activity suggests that a
force is exerted on the current-carrying aluminium rod when it is placed
in a magnetic field. It also suggests that the direction of force is also
reversed when the direction of current through the conductor is reversed.
Now change the direction of field to vertically downwards by
interchanging the two poles of the magnet. It is once again observed that

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