Electromagnetism Definitions Flashcards
Coulomb’s Law
Describes the force of attraction (or repulsion) between two charges.
Electric Field
The region that surrounds electrically charged particles in which a force is
Electrostatic Shielding
When devices which might be affected by an electric field are enclosed in a
conductive material so that the electric field inside is zero.
Electric Field Strength
The electrical force per unit positive charge.
Electrostatic Potential
The work done in moving unit positive charge from infinity to a certain point.
Electronvolt (eV)
A unit of energy, often used in high-energy particle physics.
1 eV is equivalent to 1.6x10-19 J.
Ferromagnetic
Material
A material which can become permanently magnetised. Examples include iron,
steel, cobalt and nickel.
Magnetic Field
A region of space around a magnet where another magnet will experience a
force.
Solenoid
A current-carrying wire wrapped around a soft iron core to form a coil.
Magnetic Induction
The strength of a magnetic field at a point.
Fleming’s Right Hand
Rule
Used to determine the direction of the force on a current-carrying wire, or
moving charge, in a magnetic field.
Pitch
The distance between adjacent loops in the helix after one period when a
charged particle enters a magnetic field at an angle.
Capacitor
An electronic device which stores charge and therefore energy in electrical
circuits. They are often used in circuits that require a time delay before
releasing energy.
RC Circuit
A circuit containing both a resistor and capacitor.
Time Constant
If the capacitor is charging, it is the time taken to increase the charge stored to
63% of the difference between initial charge and full charge.
If the capacitor is discharging, it is the time taken for the capacitor to discharge
to 37% of its initial charge.
Resistance
Where a device will oppose current flowing through it because of a physical
property of the device.
Reactance
Where a device will oppose current flowing through it because of a phenomena
produced when the device is working.
Capacitive Reactance
The opposition of a capacitor to changing current (i.e. a.c. current).
Electromagnetic
Induction
When a moving or varying magnetic field cuts a conductor to create an
electromotive force (e.m.f.) across it.
OR
When a conductor is moved perpendicular to a magnetic field it will generate
an e.m.f. across the conductor.
Inductor
A coil of wire which is often wrapped around an iron core.
Without an iron core, it is called an air cored inductor.
With an iron core, it is called an iron cored inductor.
Back EMF
Produced when a magnetic field is generated around the coil when an inductor
is placed in a circuit in which the current is changing.
Lenz’s Law
The induced e.m.f. always opposes the change in current which causes it.
Self-Induced EMF
When a coil induces an e.m.f. in itself due to its own changing current.
Inductance
A property of an inductor itself. It depends on its design.
Inductive Reactance
The opposition of an inductor to changing current (i.e. a.c. current)
Electromagnetic
Radiation
Exhibits wave properties as it transfers energy through space.
It has both electric and magnetic field components which oscillate in phase,
perpendicular to each other and to the direction of energy propagation.
All EM radiation travels at the speed of light in a vacuum (3x108 ms-1
).
