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PHRASAL VERBS OF THE DAY(Revision)

🌹 LAY OFF:
••This means to dismiss or sack.
••This means to stop using or doing something

The company has decided to lay off some of the casual workers

The man agreed to lay off the habit of smoking

🌹 RESORT TO:
This means to make use of an unpleasant alternative.

When the large hall was not available, we resorted to making use of the mini hall

🌹 GET BACK AT
This means to take revenge on somebody.

Bola Tinubu has vowed to get back at some of the hoodlums who destroyed home of his personal property

🌹 LEAVE OUT
To omit or exclude.

Lionel Messi's name has been left out of the Barcelona squad

🌹 BRING ROUND
This means to revive someone who has fainted

Although Ola fainted last night, he has been brought round by experienced doctors

IDIOMS OF THE DAY

These are the JAMB idioms that appeared TWICE OR MORE in the past questions and are therefore MORE LIKELY to be repeated in your JAMB this year.

🌹TELL-TALE SIGN:
••showing that something exist or has happened.
••gossip about or reveal another person's secrets or wrongdoings.

"she sparked a family row after telling tales about her mother on a TV show"

🌹THROW YOUR WEIGHT AROUND:
••to use your position or influence unfairly to get what you want.
••be unpleasantly self-assertive.

"he didn't swagger or throw his weight around"

🌹TO KEEP OPEN HOUSE:
••to have your house in a condition in which visitors are welcome at any time.
••a situation in which people welcome visitors at any time:

~We keep open house, so come and see us any time.

🌹UNDER A CLOUD:
••used to say that other people are suspicious of someone because they think he/she has done something wrong.
••under suspicion or discredited.
••Under suspicion, in trouble, or out of favor.

"he left under something of a cloud, accused of misappropriating funds"
~Ever since his brother was accused of fraud, he's been under a cloud.

🌹UP IN THE AIR:
••not yet decided.
(of a plan or issue) still to be settled; unresolved.

"the fate of the power station is up in the air"

🌹WIDE OF THE MARK:
••not accurate
••not achieving the desired result.

~Their estimates were completely wide of the mark.

Notes:

🧲 Magnets are objects that experience attraction and repulsion

🧲The ends of a magnet are called poles, So magnets have two poles: a north and a south

🧲The like poles repel (push each other apart)

For example a north pole will repel a north pole and a south pole will repel a south pole

🧲 Unlike poles attract (move towards each other)

For example a north pole will be attracted to a south pole


🧲 Only a magnet can repel another magnet, Magnetic materials (which are not magnets) will always be attracted to the magnet, while Non-magnetic materials are not attracted or repelled as they do not interact with the magnetic field

🧲 There are two types of magnets
◇ Permanent magnets
◇ Induced magnets

🧲 Permanent magnets are made out of permanent magnetic materials, for example, steel

● A permanent magnet will produce its own magnetic field, and it will not lose its magnetism


🧲On the other hand, when a magnetic material is placed in a magnetic field, the material can temporarily be turned into a magnet, This is called induced magnetism
◇ Some objects, such as paperclips or needles (which are made from steel), can be magnetised and will remain magnetic for a while
◇ Other objects, such as electromagnets or transformers (which are made from iron), will be demagnetised as soon as the cause of the induced magnetism is removed


🧲 When magnetism is induced on a material:
One end of the material will become a north pole
The other end will become a south pole

Since magnetic materials will always be attracted to a permanent magnet, This means that the end of the material closest to the magnet will have the opposite pole to magnets pole closest to the material

⭐ A magnetic field is defined as: "The region around a magnet where a force acts on another magnet or on a magnetic material (such as iron, steel, cobalt and nickel)"

OR "A region around a magnetic material or a moving electric charge within which the force of magnetism acts."


⭐ A uniform field is created when two opposite poles are held close together.

⭐ Magnetic fields are always directed from North to South

⭐ A uniform magnetic field is one that has the same strength and direction at all points

⭐ Magnetic field lines are used to represent the strength and direction of a magnetic field

⭐The direction of the magnetic field is shown using arrows
■ There are some rules that must be followed when drawing magnetic field lines.
》Magnetic field lines: Always go from north to south (indicated by an arrow midway along the line)
》 Must never touch or cross other field lines

⭐ The magnetic field is strongest at the poles, This is where the magnetic field lines are closest together

⭐The magnetic field becomes weaker as the distance from the magnet increases, This is because the magnetic field lines are getting further apart

For a circular coil carrying a current, the face of the coil at which the current is seen to flow clockwise is the S-pole while the other face is the N-pole of the magnetic field

For a solenoid (a long cylindrical coil of insulated wire) carrying a current, the direction of the Field is determined using any of the above rules

MAXWELL'S RIGHT HAND SCREW RULE: If a right handed screw is turned such that its point travels along the direction of the current, the direction of rotation of the screw is the direction of the magnetic field.


CLENCHED FIST RULE: if the wire is grasps with the right hand,such that the thumbs points in the direction of the current, the direction of the curled fingers is the direction of the magnetic field

AN ELECTRIC MOTOR

An electric motor converts electrical energy(electric current) into mechanical energy(rotational motion)

It consist of a rectangular coil of wire which can rotate freely between the poles of a permanent magnet

Electric current is supplied to the coil via a copper  split ring commutator and two carbon brushes

ELECTROMAGNET

An electromagnet is made by winding wire coils in opposite directions around the two arms of a U-shape soft iron bar

When current flows through the wire the ends of the soft iron become poles of a magnet: one a N-pole and the other a S-pole
The magnetism lasts as long as the current flows

The strength of the magnet increases if:

1. The number of turns around each of the U-bar is increased

2. The current is increased, and

3. the poles are made closer


Electromagnets are used for lifting magnetic materials, and in appliances such as electric bells and relays

The magnetism lasts as long as the current flow.

THE MOVING COIL GALVANOMETER

A galvanometer: is an instrument used for measuring small current(in the milliampere range)


THE AMMETER
An ammeter is an instrument used to measure large electric current of the order of ampere

It is connected in series with the part of the circuit where the current if to be measured

It must have very low resistance

💥 Electromagnetism
This is a phenomenon which takes place due to the interaction of both magnetic field and the electric field.
Hence, electromagnetic field is the joint interaction of electric field and magnetic field.
💥Force in an electromagnetic field
As discussed earlier that electromagnetic field is a combination of both electric and magnetic field.
Electric force = qE
q is the quantity of charge in Coulomb
E is the electric field intensity in N/C
Magnetic force = qvB
v is the velocity, B is the magnetic field strength measured in Tesla.
Thus
Electromagnetic force = q(E + vB)

A magnet is similar to a bipolar charged system in that

A. It consists of two opposite poles - the north and south poles
B. The earth's magnetic field has a south pole near the geographical north pole and a north pole near the geographical south pole
C. The force of attraction and repulsion between opposite and between like poles obeys a law for electrostatic charges
D. A and B only
E. A and C only

Which of the following elements are real magnetic materials?

A. Iron, steel and nickel
B. Copper, steel and iron
C. Lead, iron and brass
D. Glass, lead and steel
E. Stone, air and iron

Which of the following methods CANNOT be used to produce a steel magnet? The

A. Passing of an electric current through a solenoid
B. Repeated stroking of the specimen with a magnet
C. Repeated stroking of the specimen in opposite directions with magnets
D. Heating of the specimen
E. Hammering of the specimen in the earth's magnetic field

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