Electricity key terms Flashcards
Electric Charge = Coulomb
Measurement of the amount of charge in any situation
Earthing
When an object becomes charged and then ‘earthed’ by connecting to the earth , the electrons will seperate as much as possible , resulting in most of them ‘going to earth ‘
Insulator
Any substance through which an electric charge cannot flow
Conductor
A medium that allows electric charge to flow easily through it.
Coulomb’s law (1)
States that the force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them
Coulomb’s law (2)
A static charge will exert a force of attraction or repulsion on another static charge in its vicinity
Forces between charges
There is an electric force between all charged particles
Ions
Atoms with an overall charge
Positive ion
Losing e’s
Negative ion
Gain an electron
Polythene rod
Insulator
Rub with cloth to become charged negatively
Perspex rod
Conductor
Rub with a cloth and becomes positively charged
Different ways of charging bodies
Friction, rub rod with cloth
Contact , two conductors spread charge evenly by contact
Induction , put negatively charged rod close to a metal sphere free electrons are pushed to left hand side and some negative electrons leave sphere causing electrons to be positive
Static electricity in real life
Dust on tv screens
Static charge on clothes
Inducing charges
Move negative / positive rod close to
Earth metal subject
Remove earth
Remove rod
Insulator
A medium that does not allow electric charge to flow easily through it.
Electric field lines
Show the direction and strength of a force due to a positive charge in the field
Electric field strength
The force that a 1 coulomb charge would experience at a point in an electric field.
Potential difference / voltage (V) (v)
The work required to move a charge of 1 coulomb from 1 point to another.
Unless specified the second point is ground.
Electromotive Force EMF (E) (v)
Similar to voltage but created by induction.
Capacitor
A device capable of storing an electrical charge.
Current (I) (A)
A flow of charge though a conductor
Electrons, Ions, Holes
Series
A circuit where there is no split.
Parallel circuit
A circuit where there is a split.
Resistance (R) (Ω)
The ratio of potential difference across an object to the current flowing through it.
Potential divider
A circuit structure that divides a voltage between 2 sub circuits
Resistivity
The potential a material has for resistance
Length
Cross sectional area
Material
Wheatstone bridge
A circuit used to find the value of an unknown resistor via ratios
Meter bridge
Semi conductors
Materials that have a resistivity that is between a good conductor and good insulator
Semiconductor conduction intrinsic
Intrinsic
Conduction due to electrons and holes in a pure semiconductor material
Semiconductor conduction extrinsic
Increased conductivity due to the controlled addition of impurities
Semiconductor doping
The controlled addition of impurities to a semiconductor to increase conductivity
Semiconductor p-type
Silicon with doped boron to increase the amount of holes in the semiconductor. There is a surplus of free positive charges carrying particles yet charge is still 0
Semiconductor n-type
Silicon with doled phosphorus to increase the amount of free electrons in the semiconductor. There is a surplus of free negative charge carrying particles , yet the net charge is still 0
P-N junction
When a p and n semiconductor join they from a single semiconductor that allows charge to flow in one direction
Depletion layer
The region in the middle of a p-n junction that is almost void of charge carrying particles due to a voltage being created
1 ampere
1 amp is the constant current when 2 straight infinitely long parallel conductors are 1 meter
apart, in a vacuum, with negligible cross-sectional area; experience a force between them
of 2 𝑥 10−7 N/m.
Magnetic flux (Φ) (Wb)
Number of magnetic field lines passing through a surface.
Electromagnetic induction
When a change in magnetic field creates an EMF in a conductor which in turn produces a
current
Mutual induction
A change in magnetic field in 1 coil produces an EMF in another adjacent coil.
Self induction
A change in magnetic field in 1 coil produces a back EMF in itself.
Joules law
Power is inversely proportional to the current squared provided resistance is constant
rms
Root mean squared
The rms voltage is the equivalent DC voltage that would produce the same power dissipation in a resistor. For AC voltages, it represents the effective voltage.
What is meant by a.c
(Alternating Current): A current that periodically changes direction, typically sinusoidal in household electricity.
