ELECTROMAGNETS
Electromagnet
is a core of magnetic material (as iron) surrounded by a coil of wire through
which an electric current is passed to magnetize the core temporary.
SOLENOID
Solenoid s a
long coil of wire through which a current is passed to generate magnetic field
APPLICATIONS OF ELECTROMAGNETS
Electromagnets are wide
applied in;
i)
Industries, where industry electromagnets are used for picking magnetic
materials (metallic) by attraction.
ii) Electrical devices, as mostly
applied in electric bells and telephone receivers
ELECTRIC BELL
The electric bell is a
small electric device that converts electric energy into mechanical energy in
the form of sound.
Mode of action of electric bell
The step by step process
of working of electric bell is described below
·
The switch (K) is pressed and current flows through the electric
circuit.
·
The electromagnet (E) is powered and generates a magnetic field that
attracts the iron strip armature (A) towards it.
·
The striker (S) strikes the gong (bell) (B).
·
When the striking arm strikes the gong, the contact is broken and
current stops flowing through the circuit.
·
This causes the electromagnet to lose its magnetic field.
·
The connected spring arm (T) returns the striker to its original rest
position.
·
The contact is restored and current flows through the circuit.
(provided the main switch is still pressed)
·
The process is repeating from the beginning.
THE TELEPHONE RECEIVER (EARPIECE)
Telephone receiver is an electric device used for converting electrical energy into sound
energy.
When you speak to a friend
through telephone, your sound will be converted into electric current by the
mouthpiece of the telephone. The current produced is varying current and the
frequency of the current will be the same as the frequency of your sound. The
current will be sent to the earpiece of the telephone of your friend.
Mode of action of the telephone receiver
(earpiece)
The step by step process of working of electric bell is
described below
·
When the current passes
through the solenoid, the iron core become magnetized and magnetic field is
produced
·
The strength of the
magnetic field changes according to the varying current
o When the current is high, the magnetic field become stronger,
and
o When the current is low, the magnetic field become weaker
·
The soft-iron diaphragm is
pulled by the electromagnet (magnetized iron core) and vibrates at the
frequency of the varying current.
·
The air around the
diaphragm vibrates and produces sound wave.
·
The frequency of the sound
produced in the telephone earpiece will be the same as your sound.
·
This sound is what listens
by your friend.
A SIMPLE
DIRECT CURRENT (D.C) ELECTRIC MOTOR
DC Motor is an electrical
device that converts electrical energy into mechanical energy.
·
The
permanent magnet provides a constant magnetic field.
·
When the current flows through the coil (armature), the force exerted as a result of the interaction of
magnetic field and electric current
·
The force produced on the two sides of the coil is such that the coil (armature) starts to
move (rotates) in the direction of force as described by Fleming’s Left hand
rule.
·
The
armature is connected to a DC power source through a pair of commutator rings.
·
When
the current flows through the coil an electromagnetic force is produced on it,
so the coil (armature) will start to rotate.
HOW TO
IMPROVE THE EFFICIENCY OF THE D.C MOTOR?
Efficiency of a DC motor can be increased by
increasing
i)
the number
of turns in the coil
ii) the strength of the current
iii) the area of cross-section of the coil
iv) the strength of the radial magnetic field
No comments:
Post a Comment