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Electricity (IV Characteristics (Filament Bulb (S-Shape, As pd through…
Electricity
IV Characteristics
Filament Bulb
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Collisions between electrons and metal ions cause energy to be transferred from the electrons to the metal ions, heating the metal
The metal's ions vibrate faster, increasing the amount that they interact with the electrons, opposing the flow of electrons more and increases the resistance
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Same happens for negative voltages, so rotational symmetry about the origin
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Diode
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Once potential difference is greater than switch on voltage of around 0.6V the resistance becomes almost zero and the current becomes very large.
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Voltmeters are connected in parallel with a component and so ideally should have an infinite resistance
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I, V and R
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\(V=IR\)
Ohm's Law
The potential difference across an Ohmic conductor is directly proportional to the current through it, under constant physical conditions.
Potential Dividers
A pair of resistors, placed in series with a voltage source, which splits the terminal PD over the two resistors
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Can be used in invert the sensitivity of a LDR or thermistor by connected one in series with another fixed resistor, and attaching metre to fixed resistor
Potentiometers
Allow one to smoothly change the resistance of both \(R_{1}\) and \(R_{2}\) while maintaining \(R_{1}+R_{2}=R_{T}=constant\)
So that total current is same
Kirchhoff's Laws
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Circuit Rules
Series
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EMFs
Will add EMFs, taking direction of cell into account, and internal resistances will add up
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Reistivity
Resistivity of a Material \(\rho\)
The resistance of a \(1m\) length of wire of that material, with a cross sectional area of \(1m^{2}\)
Ohm Metres - \(\Omega\,m\)
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