# Module G482

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• Created by: Stacy
• Created on: 18-03-13 20:16
Conventional Current
A model used to describe the movement of charge in a circuit. Conventional Current travels from + to -
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Electron Flow
The movement of electrons (usually around a circuit), from - to +
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Equation for Charge
Charge = Current x Time, Q=It Measured in Coulombs, C
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Coulomb
Is the total charge supplied by a current of one ampere in a time of one second 1C= 1A x1s
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Kirchoff's First Law
The sum of the currents entering any junction is always equal to the sum of the currents leaving the junction (consequence of conservation of charge)
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Mean Drift Velocity
The average velocity of an electron as it travels through a wire due to a p.d
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Equation for Current/Drift velocity
I=nAve
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Potential Difference, p.d
The electircal energy transferred per unit charge when electrical energy is converted into some other form of energy
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Volt
Unit of p.d and e.m.f 1V=1J/C
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Electromotive force (e.m.f)
The electrical energy transferred per unit charge when one form of energy is converted into electrical energy, measure in volts (V)
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Resistance (R)
A property of a component that regulates the electric current through it, measure in ohms Ω
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Equation for Resistance
R= V/I
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Ohm
Unit of resistance, 1Ω= 1V/ 1A
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Ohm's Law
The electric current through a conductor is proportional to the potential difference across it, provided physical conditions, such as temperature, remain constant
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Resistivity of a material
The ratio of the product of resistance and cross-sectional area of a component and its length
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Equation for Resistivity
R=ρl/A
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Power
The rate of energy transfer
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The 3 Power Equations
P=VI or P=I²R or P=V²/R
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Equation for Energy Transfer or Work Done
W=IVt or W=I² Rt or W=V²/R t
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Kilowatt-hour
1kWh = 1000 watts for 3600 seconds
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Kirchoff's Second Law
The sum of the e.m.f is equal to the sum of the p.d in a closed loop/circuit (a form of conservation of energy)
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Terminal p.d
Of a source is the potential difference across its terminal
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Equations for e.m.f
e.m.f= I (R+r) e.m.f= V+Ir
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Equation for Potential Divider Equation
Vout=R1/ R1+R2 x Vin
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Light Dependent Resistor (LDR)
A component that changes its resistance with changes in the light intensity (dark= high resistance, light= low resistance)
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Thermistor
A component that changes its resistance depending on its temperature. An NTC thermistor's resistance reduces as the temperature increases
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Progressive Waves
A wave that travels from one place to another
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Longitudinal Waves
A wave where the oscillations are parallel to the direction of wave propagation, e.g. sound
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Transverse Waves
A wave where the oscillations are perpendicular to the direction of wave propagation, e.g water waves, electromagnetic waves, etc.
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Displacement (for waves)
the distance any part of the wave has moved from it mean/equilibrium/rest position (it can be positive or negative)
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Amplitude (for waves)
is the maximum displacement (its always positive)
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Wavelength
is the smallest distance between two points that have the same pattern of oscillation
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Period (for waves), T
is the time for one complete oscillation (s)
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Phase Difference (for waves)
the relationship between the pattern of vibration at two point. Two points that have exactly the same pattern of oscillation are said to be in phase, zero phase difference between them (radians)
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Frequency (for waves)
is the number of oscillations per unit time at any point (Hz)
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Speed of a wave
is the distance/ time for a wave, v= λ/T or v=fλ
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Reflection of waves
when waves rebound from a barrier, changing direction but remaining in the same medium
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Refraction of waves
when waves change direction when they travel from one medium to another due to a difference in the wave speed in each medium
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Diffraction of waves
when a wave spreads out after passing around an obstacle or through a gap
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Principle of superposition of waves
the principle that states that when two or more waves of the same type exist at the same place the resultant wave will be found by adding the displacements of each individual wave
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Interference
The addition of two or more waves (superposition) that results in a new wave pattern
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Coherence
Two waves with a constant phase relationship
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Path difference
The difference between the distances travelled from their sources by two waves meeting at a point.
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Constructive Interference
If two waves, A and B, exist at the same point and are travelling in phase, the amplitude of the resultant wave will be twice that of the individual waves. Produces a bright fringe.
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Destructive Interference
If two waves, A and B, exist at the same point and are travelling in anti-phase, the resultant amplitude will be zero as they shall cancel each other out
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Intensity of a wave
is the radiant power transmitted per unit cross-sectional area at right angles to the velocity of the wave
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Intensity Relationships (2)
Intensity= power/ cross-sectional area (W/m²) and Intensity∝amplitude²
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## Other cards in this set

### Card 2

#### Front

The movement of electrons (usually around a circuit), from - to +

Electron Flow

### Card 3

#### Front

Charge = Current x Time, Q=It Measured in Coulombs, C

### Card 4

#### Front

Is the total charge supplied by a current of one ampere in a time of one second 1C= 1A x1s

### Card 5

#### Front

The sum of the currents entering any junction is always equal to the sum of the currents leaving the junction (consequence of conservation of charge)