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Internal Resistance All power supplies have some resistance between their terminals This is called internal resistance (r) This internal resistance causes the charge circulating to dissipate some e...
Electromotive Force When charge passes through a power supply such as a battery, it gains electrical energy The electromotive force (e.m.f) is the amount of chemical energy converted to electrical ...
Circuit Symbols The diagrams below show the various circuit symbols that could be used in circuit diagrams. You will be expected to recognise and draw all of these The most common symbols are as fo...
Resistance in a Light-Dependent Resistor A light-dependent resistor (LDR) is a non-ohmic conductor and sensory resistor Its resistance automatically changes depending on the light energy falling on...
Resistivity All materials have some resistance to the flow of charge As free electrons move through a metal wire, they collide with ions which get in their way As a result, they transfer some, or a...
Resistance in a Filament Lamp The I-V graph for a filament lamp shows the current increasing at a proportionally slower rate than the potential difference I-V characteristics for a filament lamp Th...
I–V Characteristics As the potential difference (voltage) across a component is increased, the current also increases (by Ohm’s law) The precise relationship between voltage and current is differen...
Ohm's Law Ohm’s law states that for a conductor at a constant temperature, the current through it is proportional to the potential difference across it Constant temperature implies constant resista...
Defining Resistance Resistance is defined as the opposition to current For a given potential difference: The higher the resistance the lower the current Wires are often made from copper because cop...
