B.5 Circuits Flashcards
Current
The rate of flow of electric charge
Amount of charge symbol
q
Amount of charge units
Coulombs (C)
Current units
C/s (coulombs per sec) or A (amperes)
What are the charge carriers in electric circuits?
Electrons
What is elementary charge?
The charge of a single electron
What is direct current?
A current that flows continually in one direction
What is alternating current?
Current that reverses direction at regular intervals
Potential difference
The difference in the electric potential energy of a charge between two points
Current in a series circuit
The current is the same around the circuit
Potential difference in a series circuit
The sum of all the potential differences across the components add up to the potential difference across the power supply.
Current in a parallel circuit
The current splits up between the branches
Potential difference in a parallel circuit
The potential difference in each branch is the same
Resistance
The ratio of p.d across a component to the current flowing through a component
Resistor
A component whose resistance is constant over a range of p.d’s and currents
Ohms Law
The current flowing though a piece of metal is proportional to the p.d across it providing the temp remains constant.
Ohmic
A metal conductor at a constant temp and resistance
Non-ohmic
A metal whose resistance changes due to a temp increase
On a graph of I against V what does a straight line suggest?
Ohmic
On a graph of I against V what does a curved line suggest?
Non-ohmic
What is the resistance of an ideal ammeter?
zero
What is the resistance of an ideal voltmeter?
infinite
What do resistors convert
the electrical potential energy of the electrons flowing through them into heat energy
What is a variable resistor?
A resistor whose resistance can be changed
