# Unit 1: Electricity

Flashcards for remembering key ideas behind electricity such as current, power, resistance, series & parallel circuits, resistivity, potiental dividers, alternating current and oscilloscopes.

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Current (I)
The rate of flow of charge (A, Amperes) I= Q / t
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Potential Difference (V)
PD= WD (J) / Q (C)
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Resistance (Ω)
R= V / I
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A Volt (1V) is...
a Joule per Coulomb (1J/C)
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Conventional current goes from....
Positive to negative. Technically this is wrong, but accepted.
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Ohm's Law...
...states as long as temperature and physical conditions stay the same. Current is directly proportional to Potential Difference.
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Conductance (G) is...
Reciprocal of resistance, measured in Siemens (S). G= I / V
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A Variable Resistor....
changes the potential difference and current. (Variable power supply will also do this)
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A < 1 > must be connected in series. A < 2 > must be connected in parallel
Ammeter in series. Voltmeter in parallel.
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If the gradient on a I/V graph gets steeper...
...then the resistance must be increasing. (And vice versa)
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Diodes...
are semi-conductors only allow charge one way, forward bias. (Most have a 0.6V threshold potiental)
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A potentiometer...
allows a change of volts supplied from the battery source.
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Resistivity (ρ, Ohms M-1)...
ρ = A R / l
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Conductivity...
..is simply the inverse of Resistivity (G) = 1 / ρ
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Power is....
P= I V Note: 1 Watt= 1 Joule per 1 second
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Passive Transducers (Resistive Transducers)...
are things like LDRs, Thermistors, Strain Gauges & Moisture Detectors. They change resistance according to environmental factors.
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A Thermistor...
has a negative temperature coefficient. This is because as it warms up more energy carriers become available to carry charge.
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Potential Divider (in words..)
is used to change PD. This works by using 2 resistors in series, the fractional resistance of one resistor out of both is the way of spliting the overall PD.
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## Other cards in this set

### Card 2

#### Front

PD= WD (J) / Q (C)

#### Back

Potential Difference (V)

R= V / I

### Card 4

#### Front

a Joule per Coulomb (1J/C)

### Card 5

#### Front

Positive to negative. Technically this is wrong, but accepted.