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Physics Revision Notes
Unit 2.2 Resistance
1/21/2012

Sam Hatzigeorgiou

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Module 2.2 resistance
Electromotive force
Electromotive force (e.m.f) ­ This is the energy transferred per unit of charge when one
other type of energy is converted into electrical energy

To find an electrical current you need to know how much energy is supplied to each unit of
charge. This is…

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There are many different Electrical Abbreviations that are used. They are listed here in this
table:

Physical Quantity Abbreviation SI Unit
Time t Second s
Electric Current I Ampere A
Electric Charge Q Coulomb C
Potential difference V Volt V
Energy W Joule J
Power P Watt W


Using all…

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Resistance and Ohms Law
Ohms Law
Ohms law is a law of physics discovered in the 1820s by German Physicist George Ohm. It states that
by increasing the number of cells in a battery connected to a length of wire produced a
proportionate increase in the current flowing through the…

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The V-I characteristics of a Light emitting Diode (LED)
I diode is a simple device which lets current pass through it in 1 direction only. They can have
a large current pass through them and special ones called LED's emit light when they have
current passing through them. Advantages are:…

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The effect of temperature on restivity
Variation of resistance of a metal with temperature
The internal energy in atoms increases with temperature. As long as a material does not
melt then its volume will remain unchanged. There is also no change in potential energy,
however there is a change in…

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Domestic electrical supply
Fusing
Domestic house electricity is supplied at 230V and a current of up to 60A. This means the
maximum power that can be used at any time is 13.8Kw. The current is supplied to the
house by distribution boards. They instantly activate if there is an overload…

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