5.0 Electricity Flashcards
Define electric current
The rate of flow of charge
Define potential difference
The work done per unit charge
Current - Voltage characteristics for an ohmic conductor
Current is directly proportional to voltage, provided temperature remains constant
Current - Voltage characteristics for a semi-conductor diode (forward bias)
Current flows once forward bias voltage exceeds threshold voltage
Current - Voltage characteristics for a semi-conductor diode (reverse bias)
Current flows once reverse bias voltage exceeds breakdown voltage
Current - Voltage characteristics for a filament lamp
As voltage increases, temperature increases, increasing resistance and flattening the graph
Why does a diode have a threshold voltage?
Above a specific voltage is required to overcome the barrier of the junction
I-V graphs for a filament lamp
linear through the origin with flattening gradient with increasing absolute voltage
Define ohm’s law
Voltage is directly proportional to the current providing constant physical conditions
Define resistivity
A measure of how strongly a material opposes the flow of electric current
What is the effect of temperature on metal conductors
Increasing temperature causes more vigorous vibrations in ions, resulting in more electron collisions and so increased resistance
What is the effect of temperature on negative temperature coefficient thermistors
Increasing temperature releases more free electrons, increasing conductivity and thus reducing resistance
What are some applications of thermistors
Temperature sensors or resistance - temperature graphs
Define superconductivity
A property of a material where, below a certain temperature, the resistivity is zero
What are some applications of superconductors
The production of strong magnetic fields and the reduction of energy loss in transmission of electric power
What is conservation of charge in a DC circuit
The total charge entering a junction equals the total charge leaving the junction
What is conservation of energy in a DC circuit
The total energy supplied by the source is equal to the total energy dissipated in the components of the circuit.
What is the use of the potential divider
To supply a specific or variable
potential difference from a power supply
What is electromotive force
Electromotive force is the energy provided by a source per unit charge to move the charge through the circuit
What is the terminal pd
The voltage across the terminals of the source when current flows
What is internal resistance
Internal resistance is the resistance inside a power source that opposes the flow of current
Direction of conventional current
Positive to negative
