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Magnetism (Magnetic Field (Sources (Magnet, Magnetic field of the earth,…
Magnetism
Magnetic Field
A region around a magnet where a magnetic force can be experienced
Has two poles: North (N) and South (S)
Like poles (N-N or S-S) repel each other
Opposite poles (N-S) attract each other
Sources
Magnet
Magnetic field of the earth
Current carrying conductor
Magnetic Field Lines
Line to present Magnetic Field
Magnetic field lines leave the North Pole and enters the South Pole of a magnet
The pattern of the magnetic field lines can be determined by using two methods
compass needles
Sprinkling iron filings on paper
Magnetic flux density, B
The magnetic flux per unit area across an area at right angles to the magnetic field
vector quantity
also known as magnetic induction (magnetic field intensity OR strength)
unit is Tesla (T) OR weber per metre squared (Wb m -2)
Magnetic Field Produce by Current Carrying Conductor
The direction of magnetic field around the wire or coil can be determined by using the right hand grip rule
The magnetic field will be produced when current flows in a conductor wire or coil,
Magnetic field of a long straight conductor (wire) carrying current
The magnitude of magnetic flux density (magnetic field intensity), B at point P at distance r from the wire carrying current
Magnetic field of a circular coil
Circular shaped conductor with radius R that carries a current I
Magnetic field of a solenoid
A solenoid is an electrical device in which a long wire has been wound into a succession of closely spaced loops with geometry of a helix
Torque on The Coil
The torque is zero when = 90⁰ or ɸ= 0⁰ and is maximum when = 0⁰ or ɸ= 90⁰
Motion of Charged Particles in Magnetic Field
Consider a positively charged particle with mass m, charge q and velocity v enters a region of space where the electric and magnetic are perpendicular to the particle’s velocity and to each other
The charged particle will experiences the electric force FE is downwards with magnitude qE and the magnetic force FB is upwards with magnitude qvB
If the particle travels in a straight line with a constant velocity hence the electric and magnetic forces are equal in magnitude
Velocity selector
Normally, after the charged particle passing through the velocity selector it will enter the next region consist of a uniform magnetic field only. This apparatus known as mass spectrometer
When the charged particle entering the region consist of magnetic field only, the particle will make a semicircular path of radius r as shown in above
Magnetic Force on Moving Charged Particles in Uniform Magnetic Field
Magnetic force
A stationary electric charge in a magnetic field will not experience a magnetic force. But if the charge is moving with a velocity, v in a magnetic field, B then it will experience a magnetic force
Thumb – direction of Force
First finger – direction of Field
Second finger – direction of Velocity
When the path is a circle, therefore the magnetic force FB contributes the centripetal force FC (nett force) in this motion
The period of the circular motion
Magnetic Force on Current Carrying Conductor in Uniform Magnetic Field
When a current-carrying conductor is placed in a magnetic field B, thus a magnetic force will acts on that conductor
The direction of the magnetic force can be determined by using the Fleming’s left hand rule
The magnetic force on the conductor has its maximum value when the conductor (and therefore the current) and the magnetic field are perpendicular (at right angles) to each other then =90⁰
Magnetic Force Between Two Parallel Current-carrying Conductors
Force per unit length
Consider two identical straight conductors 1 and 2 carrying currents I1 and I2 with length l are placed parallel to each other
If the direction of current in the conductor 2 is change to upside down, the magnitude of F12 and F21 can be determined by using the equations and their direction can be determined by applying Fleming’s left hand rule
