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28 Cards in this Set
- Front
- Back
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COULOMB
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One coulomb is the amount of charge which flows past a point in a circuit in a time of 1s when current is 1A.
Q=I.t |
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ELEMENTARY CHARGE
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The smallest unit of charge that a particle or an object can have.
1.6 * 10^-19 C |
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FIRST KIRCHHOFF'S LAW
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The sum of the currents entering any point in a circuit is equal to the sum of the currents leaving the same point.
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MEAN DRIFT VELOCITY
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The average speed of charged particles along the length of a conductor .
I=Anev |
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CONVENTIONAL AND ELECTRON FLOW
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The direction of conventional current is from positive to negative; the direction
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ELECTROLYTE
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An electrically conducting solution. The conduction is due to positive and negative ions in the solution
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ELECTRICAL RESISTANCE
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The ratio of potential difference to current
R=V/I V=I*R I=V/R R= 1/(gradient of graph) |
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KILOWATT-HOUR
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The energy transferred by a 1kW device in a time of 1 hour
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LIGHT EMITTING DIODE (LED)
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A semiconductor component that emits light when it conducts.
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NUMBER DENSITY
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The number of charged particles per unit volume
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PARALLEL
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A term used when components are connected across each other in a circuit
Components connected in parallel have the same p.d. across them |
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POTENTIAL DIFFERENCE
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The energy loss per unit charge passing through a component
V=W/Q |
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POWER
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The rate at which energy is transferred; in electrical terms is the product of voltage and current.
P= VI For resistance: P= I^2 R P= V^2/R REMEMBER : E=IVt E=QV E=Pt |
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RESISTIVITY
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The property of a material defined by:
Factors: -length L -cross-sectional area A -the material the wire is made from -its temperature resistivity= (R*A)/L |
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RESISTOR
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An electrical component whose resistance in a circuit remains constant. Its resistance is independent of current or potential difference
Resistors in series have a total resistance given by: R= R1+R2+R3...+Rn Resistors connected in parallel have a total resistance given by: R= 1/R1 + 1/R2+ 1/R3 ... + 1/Rn |
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SEMICONDUCTOR DIODE
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An electrical component made from a semiconductor material (silicon) that only conducts in one direction. A diode in "reverse bias" has an infinite resistance
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SERIES
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A term used when components are connected end-to-end in a circuit
Components connected in series have the same current though them |
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THRESHOLD VOLTAGE
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The minimum forward bias voltage across a light-emitting diode (LED) when it starts to conduct and emit light
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OHM
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Is the resistance of a component when a potential difference of 1 volt is produced per ampere of current
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OHM'S LAW
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For a metallic conductor at constant temperature, the current in the conductor is directly proportional to the potential difference across its ends
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FACTOR WHICH AFFECT THE RESISTANCE OF A METAL
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Current is due to the movement of free electrons
*Temperature: ions vibrate with larger amplitudes. The electrons collide more frequently with the vibrating ions, and this decreases mean drift velocity *The presence of impurities: atoms of different sizes. It disrupts the free flow of electron. In colliding, the electrons lose energy to the vibrating atoms |
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OHMIC COMPONENTS
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Include wires at constant temperature and a resistors
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NON-OHMIC COMPONENTS
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Include filament lamp and LED
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THERMISTOR
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Component which shows a rapid charge in resistance over a narrow temperature range. The resistance of an NTC thermistor decreases as its temperature is increased
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ELECTROMOTIVE FORCE
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Energy gained per unit charge by charges passing through a supply (J/C)
E= W/Q |
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FUSES
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Device which is fitted in an electric circuit; it is usually there to protect the wiring from excessive currents
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AMMETERS
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Measure current and are connected in series. Ammeter has very small resistance
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VOLTMETER
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Measure potential difference and are connected in parallel. A voltmeter has very high resistance
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