The poles of a magnet: the places where the magnetic forces are strongest.
When two magnets are brought close together, they exert a force on each other.
Like poles repel each other. Unlike poles attract each other.
Attraction and repulsion between two magnetic poles are examples of non-contact force.
Permanent magnet: produces its own magnetic field. Always magnetic.
Induced magnet: a material that becomes a magnet when it is placed in a magnetic field. Induced magnetism always causes a force of attraction. When removed from the magnetic field an induced magnet loses most/all of its magnetism quickly.
Magnetic field: the region around a magnet where a force acts on another magnet or on a magnetic material (iron, steel, cobalt and nickel).
The strength of the magnetic field dependson the distance from the magnet. The field is strongest at the poles of the magnet.
The direction of a magnetic field line: always from north to south.
A magnetic compass contains a small bar magnet. The Earth has a magnetic field. The compass needle points in the direction of the Earth’s magnetic field.
You can plot the magnetic field of a magnet using a compass. Put the compass near the magnet. Trace where the needle points and move the compass to the new point, and keep repeating. This would allow you to draw the field lines.
Motor effect:
When we have a wire with a current flowing through it, there would be a magnetic field around it.
If the wire has a magnetic field, and it interacts with the magnetic field of a nearby permanent magnet, this causes a force.
We add a split-ring commutator to reverse the direction of the current every half turn, to allow the motor to keep spinning in the same direction.
Fleming's left hand rule: tells you the direction of the force.
Thumb: movement (force)
First finger: field
Second finger: current
The strength of the magnetic field depends on: size of current, the distance from the wire.
To increase the strength of the magnetic field: shape the wire into a solenoid (coil), add an iron core.
The magnetic field inside a solenoid is strong and uniform. and has a similar shape to that of a bar magnet.
