ELECTROMAGNETISM
ELECTROMAGNETISM:- Is the production of magnetism from electric current and electric field.
OR
Is the effect produced by the interaction of an electric current with a magnetic field.
Magnetic field:- Is a region around a conductor carrying current where magnetic effect
experienced/obtained.
Magnetic flux:- Is a measure of the amount of magnetic field passing through a given area (surface).
❖ The interaction can result in a force causing the conductor carrying-current to move.
❖ The magnetic field around a current-carrying conductor can be shown by means of magnetic field
line.
❖ The figure below shows the magnetic field pattern around a conductor.
FACTORS AFFECTING THE MAGNITUDE (STRENGTH) OF THE MAGNETIC FIELD AROUND THE CONDUCTOR CARRYING-CURRENT
i) The amount of the current.
ii) The dimensions of the conductor.
NOTE:- The higher the current, the stronger the magnetic field. Thus; the current and the dimensions of the conductors are directly proportional to the magnetic field around the conductor carrying-current.
❖ The strength of the magnetic field decreases as you move further from the conductor.
THE DIRECTION OF THE MAGNETIC FIELD
❖ The direction of the magnetic field is determined by applying two rules. These rules are as follows;
1. The Right-hand Grip Rule
2. Maxwell’s cork screw rule (The cork screw rule)
1. The Right-hand Grip Rule.
The Right-hand Grip rule can be applied to:-
▪ A straight conductor carrying-current
▪ A solenoid carrying an electric current
▪ For a straight conductor, the Right-hand Grip Rule states that;
“Imagine the wire carrying the current is gripped by the right hand, the thumb pointing in the direction of the convectional current (from positive to negative), the fingers will curl around the wire pointing in the direction of the magnetic field”.
For a solenoid, the Right-hand Grip Rule states that;-
“When you wrap your right hand around a solenoid with your fingers pointing in the direction of convectional current, your thumb points in the direction of the magnetic north pole”.
SOLENOID: - Is a coil of insulated wire which is used to produce a concentrated magnetic field
when connected in an electrical circuit.
❖ A solenoid is usually a long coil containing a large number of close turns of illustrated copper wire.
❖ The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet. The lines of magnetic force pass through the solenoid and return to the other end.
FACTORS AFFECTING THE MAGNITUDE (STRENGTH) OF THE MAGNETIC FIELD AROUND THE SOLENOID CARRYING-CURRENT
i) The number of turns in the solenoid
ii) The magnitude of the current flowing through the solenoid.
Hence;
❖ The strength of the magnetic field produced by a current-carrying solenoid is directly proportional
to the number of turns in the solenoid and the magnitude of the current flowing through the solenoid.
2. Maxwell’s Right-hand screw Rule.
It states that;- “If a right-hand screw advanced in the direction of the current, then the direction of
rotation of the screw represents the direction of the magnetic field due to the current”.
