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P2 electricity, Factors that affect ohmnic conductors, Non-Ohmic…
P2 electricity
GLOSSARY
ampere
Unit of current, eg the current in the bulb is 4 amps or amperes (A).
battery
A chemical supply of electrical energy. For example, common battery voltages include 1.5 V and 9 V.
Circuit
A closed loop through which current moves - from a power source, through a series of components, and back into the power source.
Ohms
The unit of electrical resistance, whose symbol is Ω.
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power
The energy transferred each second, measured in watts (W). Power = work done ÷ time taken.
relationship
A relationship tells us how two or more variables work together, eg the relationship between resistance, voltage and current is: resistance = voltage ÷ current.
resistance
The opposition in an electrical component to the movement of electrical charge through it. Resistance is measured in ohms.
resistor
An electrical component that restricts the flow of electrical charge. Fixed-value resistors do not change their resistance, but with variable resistors it is possible to vary the resistance.
series
A circuit where one component follows directly from another, eg three bulbs in a row with no junctions are said to be connected in series.
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voltage
The potential difference across a cell, electrical supply or electrical component. It is measured in volts (V).
thermistor
A resistance thermometer, or a resistor whose resistance is dependent on temperature.
ACDC and pugs
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DC - typically used in a series circuit and is produced from a cell, it goes on way
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Oscilloscope - used to see current and shows us the maximum potential difference. We can use this to calculate frequency
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Live wire, a neutral wire and the earth wire
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Brown wire is the live wire, cover the potential difference, connected to a fuse in the plug
Blue wire is the neutral wire, it completes the circuit, has no potential difference
Green wire is the earth wire, stops an appliance from becoming life (having potential difference)
Live wire carries the electric current, live wire is connected to the fuse, neutral completes the circuit.
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CHANGING STATE
The hotter a solid is, the faster its particles vibrate
Eventually, the vibrations will be so strong that the particles begin to break free from their neighbours
At this point, the solid starts to melt and become a liquid
The hotter a liquid is, the faster its articles move around
As the temperature rises, more and more energy is transferred from the surroundings to the particles and the particles escape from the surface of the liquid – its rate of evaporation increases
Eventually, the liquid boils and bubbles of gas rise and escape from within the liquid
Each change of state is reversible, they are examples of physical changes
No new substance is formed during a change of state – water molecules, H20, are the same in ice as they are in liquid water or steam
It is just the movement and arrangement of the particles that differ and affect the properties of the substances at different temperatures, not any change in the particles substances
Substances with higher melting and boiling points have stronger forces operating between their particles
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GASES
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The hotter the gas, the faster the
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LIQUIDS
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Particles are close together, but they can move past each other
This results in a constantly changing, random arrangement of particles
ELECTRIC FEILDS
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The further away from the object, the weaker the charge of the field
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MELTING POINTS
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The hotter an object is , the faster its particles vibrate.
Eventually the vibrations will be so strong that the particles begin to break free from their neighbours.
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BOILING POINTS
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The hotter a liquid is, the faster its particles vibrate.
As the temperature rises more and more energy is transferred from the surroundings to the particles and the particles escape from the surface of the liquid (evaporation).
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Producing static charge
When certain insulating materials are rubbed against each other, they become electrically charged
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thermistors - at low temperatures have high resistance and at high temperatures have low resistance commonly used in fire alarms
ldr - are used to detect light levels in the dark their resistance is high and in the light their resistance is low commonly used in automatic security lights
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