Resistance, Resistivity and Practical Circuits Flashcards
Practical circuits from flashcard 13
I-V characteristic
A graph of current against voltage for a particular component of an electrical circuit
Resistor
An electrical component whose resistance in a circuit remains constant, is independent of current or potential difference
Ohm’s Law definition
A conductor obeys Ohm’s law if the current in it is directly proportional to the potential difference across its ends
Ohmic definition
A component that obeys Ohm’s law
Non-ohmic definition
A component that does not obey Ohm’s law
NTC thermistor meaning
A device whose resistance decreases rapidly when the temperature increases
Threshold voltage
The minimum forward potential difference across a diode at which it starts to conduct
Note on diode
Most modern diodes are made from silicon and will start conducting when there is a potential difference of about 0.6V across them. You need to remember this key 0.6V value.
Light-dependant-resistor meaning
A component whose resistance decreases when the light intensity increases
Delocalised electron meaning
An electron that is not attached to a specific ion, but is free to move throughout the crystal lattice
Resistivity meaning
A property of a material; it is a measure of its electrical resistance, defined by ρ = RA/L, unit Ω
Resistance equation
R = ρL/A
resistivity = (resistance x length) / cross sectional area
Internal resistance meaning
The internal resistance of a source of emf is the resistance inherent in the source itself; some energy is transferred into other forms as work is done in driving charge through the source itself
Terminal pd
the potential difference across the terminals of a source and is dependant on the current that is taken from the source
Potential difference across a power source equation
V = E - Ir
