MAGNETISM
Mr Mc Millan
TOPICS
● MAGNETISM
Permanent Magnets
Magnetic Forces
● ELECTROMAGNETISM
Electromagnetic Force
Motors
Induced e.m.f.
Transformers
MAGNETISM
Magnetism is a physical
phenomenon produced due to the
motion of electric charge. When
magnetised, magnetic materials
can attract and repel each other
and can attract magnetic
substances that are initially in an
unmagnetised state.
Magnetic and Non-Magnetic Materials
A magnetic material is a substance that is attracted to a magnet, like iron, nickel, and cobalt,
while a nonmagnetic material is a substance that is not attracted to a magnet, like plastic,
wood, rubber, and copper; essentially, anything that isn't iron, nickel, or cobalt is considered
nonmagnetic.
Temporary and Permanent Magnets
A temporary magnet/electromagnet is a material that only exhibits magnetic properties
when placed within a magnetic field, losing its magnetism once removed, while a
permanent magnet retains its magnetic properties even after the external magnetic field
is removed.
Essentially, a temporary magnet needs to be constantly exposed to a magnetic field to
stay magnetic, whereas a permanent magnet does not.
Magnet Attracts an Unmagnetized Object
A magnet attracts an unmagnetized object by inducing a temporary magnetic field within
the object, making it a temporary magnet itself. This happens because the magnet's
magnetic field aligns the microscopic magnetic domains within the unmagnetized
object,This happens because the magnet's magnetic field aligns the microscopic
magnetic domains within the unmagnetized object, causing the object to temporarily
exhibit a net magnetic field and thus be attracted to the magnet.
Magnetic Pole
A magnetic pole is the part of a magnet that exerts the strongest force on other
magnets or magnetic material, such as iron. For example, the poles of the bar magnet
shown below where the paper clips are concentrated. This is also referred to as a
dipole magnet.
Please watch….https://www.youtube.com/watch?v=5FQCEJ8XQYc
Magnetic Forces
Magnetic Field
The magnetic field is the area around a magnet in which the effect of magnetism is felt. It
is a region in which a body experiences a force due to its magnetic polarity. A magnetic
field is invisible, but it can be detected using a magnetic compass.
Magnetic field lines flow from the north pole of a magnet to the south pole outside the
magnet, and from the south pole to the north pole inside the magnet; essentially forming
a continuous loop with no beginning or end.
Please Watch…
https://www.youtube.com/watch?v=3elpPfyHV0E
https://www.youtube.com/watch?v=NWUgK8W-4JM
Please Watch…https://youtube.com/shorts/_B912lxTmHk?si=kh-hPo5PgZktpALk
ELECTROMAGNETISM
Electromagnetism is a branch of Physics, that deals with the electromagnetic force that
occurs between electrically charged particles.
Electromagnetism is a process where a magnetic field is created by introducing the
current in the conductor.
When a conductor is electrically charged it generates magnetic lines.
Magnetic Field Pattern Around Current-carrying
Conductors
Straight conductors,
Flat coils,
Solenoids.
Please watch the attach video…https://www.youtube.com/watch?v=NEd4eYfGIT4
Right Hand Grip Rule
The Right Hand Grip Rule, is
used to determine the direction
of a magnetic field around a
current-carrying wire. When you
point your right thumb in the
direction of the current flow and
curl your fingers around the wire,
the direction of your fingers will
show the direction of the magnetic
field lines.
https://www.youtube.com/watch?v=
TvO22gItg5s
Use Key and point your thumb finger in the desired direction.
X - your thumb should be facing downwards
Dot - you thumb should be facing upwards
Use the two videos attached
in the past four slides to aid
in your understanding of the
past four slides.
Commercial Application of an Electromagnet
Some major uses of electromagnets are in motors, loudspeakers, electric bells,
magnetic lifting devices, and medical devices.
Electromagnetic Force
The electromagnetic force is a force that acts between charged particles and is a
combination of electrical and magnetic forces.
A current-carrying conductor placed in a magnetic field experiences a force due to
the interaction between the magnetic field generated by the current and the
external magnetic field.
Remember, the direction of magnetic field goes from north to south.
Fleming’s Left Hand Rule
Fleming's Left-Hand Rule is a mnemonic device used to determine the
direction of the force on a current-carrying conductor within a magnetic
field. It's commonly used to understand how Electric Motors Work.
https://www.youtube.com/watch?v=qvB1mmfo7MQ
How it Works
1. Orient your left hand: Extend your thumb, index
finger, and middle finger so they are mutually
perpendicular and at right angles to each other.
2. Thumb: Points in the direction of the force
acting on the conductor.
3. Index finger: Points in the direction of the
magnetic field.
4. Middle finger: Points in the direction of the
conventional current flow (from positive to
negative).
Interference of a line of Magnetic Force
The magnetic fields produced by the current and the
permanent magnets interfere each other.
The line of magnetic force distributed in the same
direction acts to increase its strength, while tin the
opposite direction it acts to reduce its strength.
Remember the key from slide 16
Electromagnetic Force Production
The line of magnetic force has a nature to return to
the straight line by its tension like an elastic band.
Watch..https://www.youtube.com/watc
Thus, the conductor is forced to move from where h?v=wtgSUrrph10
the magnetic force is stronger to where it is weaker
Factors that affect the force on a current-carrying conductor in
a Magnetic Field
● The strength of the magnetic field in which the current is immersed
● The magnitude of the current
● The length of the conducting wire
Increasing any of these will result in an increase in the magnitude of the
electromagnetic force.
Motors
When the motor is powered by DC
current, a magnetic field is created
within the stator, attracting and
repelling the magnets on the rotor.
This causes the rotor to start rotating.
To keep the rotor rotating, the motor
has a commutator.
Please
watch…https://www.youtube.com/watc
h?v=evWpDrRAyCc&t=25s
INDUCED Electromotive Force, e.m.f.
A voltage generated within a conductor or coil when it is exposed to a changing
magnetic field. This phenomenon, known as electromagnetic induction, is
governed by Faraday's law of induction. In the diagram below when the magnet is moved
back and forth through the coil and emf/current is produced.
https://www.youtube.com/watch?v=tC6E9J925pY
Direction of the Induced Current
Electromagnetic
The direction of the induced current in a conductor
Induction`
moving through a magnetic field is determined by
Fleming's right-hand rule in Generators. It is
used for Electromagnetic Induction.
This rule states that if you hold your right hand
with your thumb, forefinger, and middle finger
perpendicular to each other, then the thumb points
in the direction of the conductor's motion, the
forefinger points in the direction of the magnetic
field, and the middle finger points in the direction
of the induced current.
Right Hand Generator Rule
Please watch…https://www.youtube.com/watch?v=OJ9cWa_2bCo
Transformers
A transformer is a device that increases
or decreases an alternating voltage
thus an alternating current.
Transformers that increase the voltage
are called step-up transformers and
those that decrease the voltage are
called step down transformers.
Operation of a Transformer
A transformer operates on the principle of
electromagnetic induction, using an
alternating current (AC) to create a
changing magnetic field in a core. This
changing field induces a voltage in a
secondary coil, transferring electrical energy
without a direct electrical connection. The
ratio of turns in the primary and secondary
coils determines whether the transformer
steps up or steps down the voltage.
https://www.youtube.com/watch?v=7RtBUEZbKmI
Advantages of using A.C. for transferring Electrical Energy
via Transformers
AC (Alternating Current) offers several advantages for
transferring electrical energy, primarily due to its ease of
voltage transformation and efficient long-distance
transmission. AC can be readily stepped up or down
in voltage using transformers, making it suitable for
both high-voltage transmission and safe
low-voltage distribution. This flexibility minimizes
energy loss during transmission over long
distances.
The Ideal Transformer Formula
P - power in, Watts, W
V - voltage, Volts, V
I - current, Amperes, A
N - number of turns, n
p - primary coil of turns
s - secondary coil or turns
Watch these following videos to understand the formula.
https://www.youtube.com/watch?v=IxqUjM8cOcU
https://www.youtube.com/watch?v=GJm-FOMeG4E
https://www.youtube.com/watch?v=qRiMFmILd8k
