Electrons, Waves and Photons definitions Flashcards
Conductors
A material that allows the flow of electrical charge. Good conductors have a larger amount of free charge carriers to carry a current
Conservation of charge
The total charge in a system cannot change
Coulomb
The unit of charge
Electric current
The rate of flow of charge in a circuit
Electrolytes
Substances that contain ions that when dissolved in a solution, act as charge carriers and allow current to flow
Electron flow
The opposite direction to conventional current flow. Electrons flow from negative to positive
Elementary charge
The smallest possible charge, equal to the charge of an electron
Insulators
A material that has no free charge carriers and so doesn’t allow the flow of electrical charge
Kirchhoff’s first law
A consequence of the conservation of charge. The total current entering a junction must equal the total current leaving it
Mean drift velocity
The average velocity of an electron passing through an object. It is proportional to current and inversely proportional to the number of charge carriers and the cross-sectional area of the object
Quantisation of charge
The idea that charge can only exist in discrete packets of multiples of the elementary charge
Semiconductors
A material that has the ability to change its number of charge carriers, and so its ability to conduct electricity. Light dependent resistors and thermistors are both examples
Diode
A component that allows current through in one direction only. In the correct direction, diodes have a threshold voltage (typically 0.6 V) above which current can flow
Electromotive force
The energy supplied by a source per unit charge passing through the source, measured in volts
Filament lamp
A bulb consisting of a metal filament, that heats up and glows to produce light. As the filament increases in temperature, its resistance increases since the metal ions vibrate more and make it harder for the charge carriers to pass through
I-V characteristics
Plots of current against voltage, that shows how different components behave
Kilowatt-Hour
A unit of electrical energy. It is usually used to measure domestic power consumption
Light-Dependent Resistor
A light sensitive semiconductor whose resistance increases when light intensity decreases
Ohm
The unit of resistance
Ohmic conductor
A conductor for which the current flow is directly proportional to the potential difference across it, when under constant physical conditions
Ohm’s Law
The current and potential difference through an ohmic conductor held under constant physical conditions are directly proportional, with the constant of proportionality being resistance
Potential difference
The difference in electrical potential between two points in a circuit. It is also the work done per coulomb to move a charge from the lower potential point to the higher potential point. It is measured in volts
Power
The rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. It is measured in Watts
Resistance
A measure of how difficult it is for current to flow through a material
Resistivity
A measure of how difficult it is for charge to travel through a material. It is proportional to the object’s length and cross-sectional area. It is measured in Ohm metres
Resistor
A device that has a fixed resistance and follows Ohm’s law
Volt
The unit of potential difference