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Summary GCSE OCR Gateway Physics P4 Magnetism Definitions
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Definitions for the 'P4: Magnetism' topic of the GCSE OCR Gateway Spec. Fully detailed, easy to understand & perfect definitions for use in the exams.
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P4 Magnetism Definitions:Alternating current- current flow consisting of charges that continually change direction.
These oscillations usually occur at a set frequency.
Alternator- a device that makes use of the generator effect to generate alternating current.
Current-carrying wires- when current flows through a wire, a magnetic field is generated
around it. The strength of the field depends on the magnitude of the current and the
distance from the wire.
Dynamo- a device that makes use of the generator effect to generate direct current.
Electric motor- a current-carrying coil of wire in a magnetic field. The two sides of the coil
that are perpendicular to the magnetic field experience forces in opposite directions,
causing rotation.
Electromagnet- a solenoid with an iron core.
Fleming’s Left-Hand Rule- a rule used to determine the orientation of the force (thumb),
current (second finger) and magnetic field (first finger) when a current-carrying wire is
placed in a magnetic field (motor effect).
Force on a wire- when a current-carrying wire is placed perpendicular to a magnetic
field, a force is exerted on it. The force is proportional to the magnetic flux density of
the field and proportional to the current and length of the wire.
Generator effect- when there is relative motion between an electrical conductor and a
magnetic field, a potential difference will be induced across the ends of the conductor.
A current will flow if this conductor is part of a complete circuit.
Induced magnet- a material that becomes a magnet when it is placed in an existing
magnetic field, but loses its magnetism quickly once it is removed. Induced magnetism
always produces attractive forces.
Like magnetic poles- when matching poles of a magnet are brought near each other they
repel each other.
Loudspeaker- a device that converts variations in current into vibrations of a diaphragm to
produce corresponding sound waves.
Magnetic field- the region around a magnet in which another magnet or magnetic material
will experience a non-contact force.
Magnetic materials- iron, steel, cobalt and nickel.
Magnetic poles- the regions of a magnet where the magnetic forces are at their strongest.
Microphone- a device that converts the pressure variations in sound into corresponding
current variations.
Permanent magnet- a magnet that produces its own magnetic field.
Power cables- metal wires that are part of the National Grid. Electricity is transported along
them at very high voltages to reduce the energy loss and make the transportation more
efficient.
Right-hand rule- a method for determining the direction of the magnetic field produced
around a current-carrying wire. Point your thumb in the direction of the conventional
current flow and the direction that your fingers wrap around the wire determines the
direction of the field lines.
Solenoid- a wire wrapped into the shape of a coil, that has a strong and uniform magnetic
field inside of it. The solenoid’s magnetic field strength can be increased by adding an iron
core.
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