3. 3
There is an induced current in a
closed conducting loop if and only
if the magnetic flux through the
loop is changing. The direction
of the induced current is such that
the induced magnetic field always
opposes the change in the flux.
4. 4
Lenz’s law obeys the law of conservation of energy
and if the direction of the magnetic field that
creates the current and the magnetic field of
the current in a conductor are in same direction,
then these two magnetic fields would add up and
produce the current of twice the magnitude and this
would in turn create more magnetic field, which
will cause more current and this process continuing
on and on leads to violation of the law of
conservation of energy.
5. If you wrap
your fingers
around the coil
in the direction
of the current,
your thumb
points north.
5
8. 8
2 Direction of induced current
In both cases, magnet
moves against a
force.
Work is done during
the motion & it is
transferred as electrical
energy.
Induced I always flows to oppose the
movement which started it.
b Lenz's law
8
9. 9
Current induced along a coil
Indicate the direction of the induced I. Explain.
(i)
When magnet’s N-pole is moving
into coil,
induced I flows in such a direction as
to produce a N-pole
to oppose the approaching of magnet.
Lenz’
s law
I
S N
10. 10
Current induced along a coil
Indicate the direction of the induced I. Explain.
(iii)
When magnet’s S-pole is leaving the coil,
induced I flows in such a direction as to
produce a N-pole to oppose the leaving of
magnet.
I
N S
12. The changing magnetic
field in the coil due to the
change in current induces
a current in the metal ring.
Lenz’s Law states that the
magnetic field in the ring
opposes the magnetic field
of the coil and forces the
ring to fly away.
12
13. The copper tube
"sees" a changing
magnetic field from
the falling magnet.
This changing
magnetic field
induces a current
in the copper tube.
The induced
current in the
copper tube
creates its own
magnetic field that
opposes the
magnetic field that 13
