P7 - magnetism and electromagnetism

Permanent Magnet

A magnet that has its own magnetic field, exemplified by a bar magnet

Induced Magnet

A magnetic material, like iron, that becomes a magnet when placed in a magnetic field but looses its magnetic field when the permanent magnet is removed

North and South Poles

The two poles of a magnet, where the north is attracted to the south, and like poles repel each other.

Attraction and Repulsion

magnets only attract magnetic materials regardless of the poles, they do not repell. They only repell the alike pole of another magnet e.g south and south will repell

Vector Quantities

Both magnetic fields and forces are classified as vector quantities, indicating they have both direction and magnitude, which can be shown on magnetic field lines, the closeness of the lines showing the strength and the direction showing which way the force is acting

Compass

uses a bar magnet which is attracted to the south pole of any magnetic field it is near to, making it point in that direction

Earth's Core

Generates its own magnetic field, which is why compasses point north.

Right-Hand Thumb Rule

A method to determine the direction of a magnetic field from current; if the thumb points in the direction of current, fingers curl in the direction of the magnetic field.

Proportionality in Current and Magnetic Field

A larger current creates a larger magnetic field due to more moving electrons - directly proportional

Spin of Electrons in a current

Electrons have a spin that produces tiny magnetic fields, contributing to the overall magnetic field when aligned - the electrons produce the magnetic fields in a current

Solenoid

A wire wrapped in a coil; acts like an induced magnet only when current flows through it, as the electrons spin creating their own tiny magnetic fields

Bar Magnet Field Representation

The magnetic field of a solenoid resembles that of a bar magnet, with field lines emanating from each end.

Field Lines Inside Solenoid

Magnetic field inside a solenoid is strong and uniform, while outside it resembles a bar magnet's field.

Soft Iron Core in Solenoid

Adding a soft iron core increases the strength of the solenoid's magnetic field, it becomes an induced magnet when inside the coil, adding another magnetic field so making it stronger

Electromagnetism Definition

A solenoid with a soft iron core acts as an electromagnet when current flows but loses magnetism when current ceases, as it then looses its magnetic field

Motor Effect

When a current-carrying wire is placed between magnetic poles, it experiences force due to field interaction, causing the wire to move

Optimal Wire Position in Magnetic Field

The wire must be at 90 degrees (perpendicular) to the magnetic field to feel the maximum force, at paralell it will feel no force and at angles in between it will feel some

Size of Magnetic Field

Increases with the strength of the force and current flowing through the conductor.

Horseshoe Magnet Experiment

the horseshoe magnet is a permanent magnet which exerts a force on a bar, the bar completes a circuit, as the rails on which it is placed carries a current. the magnetic field produced by the bar interacts with the one produced by the magnets, causing the bar to roll along the rails.

Force Calculation in a Magnetic Field

Calculated using the formula: Force (N) = Magnetic Flux Density (T) x Current (A) x Length (m).

Fleming's Left-Hand Rule

Method for determining the direction of a force on a current-carrying conductor in a magnetic field.

Components of Fleming's Left-Hand Rule

First finger - magnetic field direction, second finger - current direction, thumb - force/motion direction.

Split-Ring Commutator

Used in motors to reverse current direction at the right times, allowing continuous rotation of the coil, which allows it to work

Coil function in Motors

Contains current that produces a magnetic field, interacting with a permanent magnet or electromagnets.

Motor Rotation Mechanism

The interaction between the coil's magnetic field and external fields causes the coil to rotate.

Reversed Current and Force Relation

Reversing current or magnetic field will reverse the direction of force/motion.

Constant Current Direction

Ensures continuous force pushing the coil in the same direction to maintain motor operation.

Electric Motor Functionality

Relies on the interaction of magnetic fields created by currents in conductors and the effects of magnetic poles.

Strength of Induced Magnets

Induced magnets are only magnetic while current is flowing through them.

Direction of Magnetic Fields

Magnetic fields run from the north pole to the south pole of a magnet.

Electromagnet vs Permanent Magnet

Electromagnets require current to maintain magnetism, while permanent magnets continuously have a magnetic field.