Magnetic field due to different shaped current carrying conductors- P10 13.02
THE PHYSICS CAFE 
CHAPTER THIRTEEN – MAGNETIC EFFECTS OF ELECTRIC CURRENT
13.02 Magnetic field due to different shaped current carrying conductors
A compass was placed near a current
carrying wire and observed
|
Switch |
Current
in wire |
Deflection
in compass |
|
Switch
off |
I
= 0 |
nil |
|
Switch on |
I
≠ 0 |
Deflect |
|
Switch off |
I
= 0 |
nil |
|
Switch on |
I
≠ 0 |
Deflect |
Direction of current is changed in the
wire
|
Switch |
Current
in wire |
Deflection
in compass |
|
Switch
off |
I
= 0 |
nil |
|
Switch on |
I
≠ 0 |
Deflect(opposite
to previous case) |
|
Switch off |
I
= 0 |
nil |
Conclusion: Needle of compass is a
small bar magnet and it can deflect only when we take other magnet near it but
in this experiment nothing was changed else current; here the current was doing
the work of a magnet, so we can say current can produce magnet like effect and
this magnet like effect by current is called Electromagnetism. So this experiment connect electricity and
magnetism with each other
The Effect of attraction or repulsion
on a magnet by a magnet is called Magnetism
The Effect of attraction or repulsion
on a magnet by electric current is called Electromagnetism
Now it become interesting
as well as important to study that
- On
which factors this magnetic field depends
- How
we can find the direction of magnetic field
- Is
different shaped, current carrying conductor produce same or different magnetic
field
Magnetic field due to a current carrying straight wire:
Let I current is flowing in the
straight wire; we observed
- Concentric
circles (magnetic field is circular and circles are concentric circles)
- As
we move away from the wire separation between circles become larger
- These
circles are in a plane perpendicular to the wire
- Direction
of Magnetic field can be find out by Right hand rule
- Magnetic
field at any point depends on
Current – directly
proportional
Radius of magnetic
circle – inversely proportional
Let I current is flowing in circular
loop; we observed
- Concentric
circles (magnetic field is circular and circles are concentric circles)
- Outside;
as we move away from the wire separation between circles become larger and
inside; magnetic field line is more; closer to the center
- These
circles are in a plane perpendicular to the wire
- Direction
of Magnetic field can be find out by Right hand rule
- Magnetic
field at the centre of circular loop depends on
Current – directly
proportional
Radius of circular
loop – inversely proportional
Number of turns -
directly proportional
Hint: Loop versus coil
versus solenoid
If number of turn is one,
called loop
If number of turns are more,
called coil
A closely wound coil of
insulated copper wire is called solenoid
Magnetic field due to a
current carrying solenoid
Solenoid: A closely wound
coil of insulated copper wire
Let I current is flowing in the
solenoid; we observed
- Magnetic
field inside a solenoid is uniform (parallel and equi-spaced lines)
- Direction
of Magnetic field can be find out by Right hand rule
- One
end become north and other south and magnet field lines pattern become same like of bar magnet
- Magnetic
field at the centre of circular loop depends on
Current – directly
proportional
Radius of circular
loop – inversely proportional
Number of turns -
directly proportional
If a Magnetic material as a core is
inserted inside a solenoid now it is called Electromagnet
- Nature
of core material – soft iron core produce stronger magnetic field
Q. Why electromagnet is
better than permanent magnet?
|
Permanent magnet |
Electro-magnet |
|
It’s
magnetism become weaker as time passes |
They
don’t lose magnetism for a long time.
|
|
It’s
magnetism is permanent |
It’s
magnetism can be removed by switching off the current |
|
It’s
magnetism is fixed |
Its
magnetism can be controlled by no. of turns or current |
|
Polarity
is fixed |
Polarity
can be change by changing the direction of current |
|
It
produces weak magnetic force |
It
produces strong magnetic force as compared to the permanent magnet |
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