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Chapter 9 Electricity - Coggle Diagram
Chapter 9 Electricity
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For a current-carrying conductor I= Anvq, where
n is the number density of charge carriers and v is the mean drift speed of charge carriers.
The resistance of a filament in a lamp increases
with increasing current because higher currents cause the temperature of the filament to increase
Charge on charge carriers is quantised in integer multiples of the fundamental charge on the electron,e,1.6x10-19C.
For a metallic conductor at constant temperature
the I-V graph is a straight line through the origin, showing it obeys Ohm's law.
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The I-V graph for a diode has a zero current for reverse bias (very high resistance).For low voltages in forward bias the current is still zero As the voltage increases (above about 0.5V)the current in the diode increases.The graph is almost a straight line.How ever the resistance is not constant but is decreasing showing that the diode does not obey 0hm's law.
Ohm's law: for a metallic conductor
at constant temperature, the current in the conductor is proportional to the potential difference across it.
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The I-V graph for a filament lamp has a constant gradient for low voltages and a decreasing gradient (showing an increase in resistance)for higher voltages, hence the filament does not obey Ohm's law.
A diode has a low resistance when connected in
forward bias, and a very high resistance in reverse bias.
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Resistivity p of a conductor of length L and cross- sectional area A is given by the equation:R=pL/A
The resistance of a negative temperature
coefficient thermistor decreases with increasing temperature.
The resistance of a metallic conductor increases with increasing temperature the resistance of a semiconductor decreases with increasing temperature.
Conventional current is defined as a flow of positive charge from positive to negative. In metals, the charge carriers are electrons, which travel from negative to positive.
The I-V characteristic of an electrical component
is a graph of current against potential difference; the shape of the graph is characteristic for different components.