the earth is a giant magnet magnetic field lines of force leave the north pole and enter the south...
TRANSCRIPT
The earth is a giant magnetMagnetic field lines of force leave the north pole and enterthe south pole. What is a magnetic field?
Magnetic field
The space around a magnet where the forces of attraction and repulsion act is the magnetic field. A magnetic
field is made up of lines of force.
What are poles?
The poles represent the part of a magnetic field where the magnetic forces appear to be concentrated.
Magnetic?
Iron steel
cobaltnickel
These materials along with certain other alloys are
called ferromagnetic materials.
Hard or soft?
Iron is a magnetically soft material. Strong but temporary!Steel is a magnetically hard material. Weak but permanent!
Making magnetsSingle touch method
The end where the stroking pole leaves the bar becomes the opposite pole.
Making magnetsDouble touch method
The end where the stroking pole leaves the bar becomes the opposite pole.
Making magnets: can a magnet have similar poles at its ends?
Consequent poles
The end where the stroking pole leaves the bar becomes the opposite pole.
The Domain Theory of magnets
Magnetic material In demagnetized condition
Magnetic material In magnetized condition
Dipoles in magnetic domains
Domain theory explains:1.Demagnetization: mechanical vibrations can
cause demagnetization2. Magnetic saturation: strength of a magnet
cannot be increased beyond a certain limit.3. Breaking a magnet: breaking a magnet the broken ends maintain the poles.
electromagnet
To tell the poles: 1. face the coil, trace the direction of current flow, if it is anticlockwise then that is the North poleIf it is clockwise then that is the South pole2.Use right hand grip rule, the thumb points to the N, the end is the S
Direction of the magnetic field
The right hand grip rule
Grip the wire with your right hand, the field lines will go in the direction of the fingers.
Magnetic effect of an electric current
Magnetic flux pattern due to a currentin a long straight wire,
Magnetic flux pattern due to a currentin a short circular coil of wire.
Magnetic effect of an electric current
Use the right hand grip rule
Magnetic effect of an electric currentMagnetic flux pattern due to a current in a solenoid.Grip the solenoid
with the right handwith the fingers in the directionof the currentThe thumb points to the north pole
Direction of the magnetic field
The right hand grip rule
Grip the wire with your right hand, the field lines will go in the direction of the fingers.
Force on conductor
Field due to permanent
magnet
Field due to current in wire
Two fields interact to produce
force (motion)