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Summary GCSE OCR Gateway Physics P3 Electricity Definitions
Definitions for the 'P3: Electricity' topic of the GCSE OCR Gateway Spec. Fully detailed, easy to understand & perfect definitions for use in the exams.
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P3 Electricity Definitions:Ammeter- a device connected in series with a component to measure the current that flows
through it.
Amperes- the unit of current.
Charge- a property of all matter. Charges can be positive or negative.
Coulomb- the unit of charge.
Diode- a component that only allows current to flow through in the forward direction. They
have very large resistances in the reverse direction.
Direct current- current flow consisting of charges flowing in a single direction only. Batteries
and cells provide direct current.
Earthing- the removal of excess charge by providing a low resistance path for electrons to
flow through.
Electric current- the rate of flow of electrical charge. Its value is the same at any position in
a single closed loop. In metals, the charges that flow are electrons.
Electric field- a region in which a charge will experience a non-contact, electric force. All
charged objects have an electric field around them, and this field is stronger the closer you
are to the charge.
Filament lamp- a light emitting component consisting of an enclosed metal filament. Its
resistance increases as the filament’s temperature increases.
Light Dependent Resistor (LDR)- a light sensitive component whose resistance decreases
as its temperature increases.
Light Emitting Diode (LED)- a device that gives out light when a current flows through it.
Current can only flow through it in one direction, and a minimum voltage must be applied
across it before it illuminates.
Lightning- static charge building up in the clouds. Lightning strikes are caused by the
discharge of this charge.
Like charges- when two charges of the same polarity meet, they will repel.
Ohmic conductor- a conductor whose current flow is directly proportional to the potential
difference across it, when held at a constant temperature.
Ohms- the unit of resistance.
Ohm’s Law- the current flowing through an Ohmic conductor at constant temperature is
directly proportional to the potential difference across it.
Parallel plates- the electric field between two charged plates is uniform. The field lines are
parallel, equally spaced and point from the positive plate to the negative plate.
Parallel- components connected in parallel have the same potential difference across each
component. The total current is equal to the sum of the currents flowing through each
component.
Point charge- the electric field around a point charge becomes weaker the further away
you are. The field lines for a positive charge point radially outwards, whereas the field lines
for a negative charge point radially inwards.
Potential difference- the energy that is transferred per unit charge between two points in a
circuit. It is often also called a voltage.
Power- the rate at which an appliance transfers energy. For a circuit component, it is equal
to the product of the current passing through it and the potential difference across it.
Series- components connected in series have the same current passing through each
component but share the total potential difference of the power supply.
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