Current, Potential Difference And Resistance Flashcards
Give an example do current in a wire
Like WATER flowing in a PIPE
The amount of water that flows depends on the flow rate and the time
What is current
Rate of flow of charge
What is the equation linking current to charge and time
I=Q/T
What direction does conventional current flow
From + to -
The OPPOSITE way from ELECTRON flow
What is one coulomb defined as
The amount of CHARGE that passes in 1 SECONDS when the CURRENT is 1 amperes
What is the potential difference defined as
Energy converted per unit charge moved
To make electric charge flow through a conductor what do you need to do on it
Work
What is the pd in the water analogy
The pressure that’s forcing water along the pipe
What is the equation linking voltage to energy and charge
V=W/Q
When is the potential difference across a component 1 volt
When you convert 1 joule of energy moving 1 coulomb of charge through the component
How much current you get for a particular pd depends on heat
The resistance of the component
What can you think of a components resistance as
A measure of how DIFFICULT it is to get a CURRENT to FLOW through it
What is the equation which links resistance to voltage and current
R=V/I
When does a component have a distance of 1
If it’s pd of 1V makes a current of 1A flow through it
For an ohmic conductor what is constant
The resistance
What is ohm’s law
Provided the TEMPERATURE is constant, the CURRENT through an ohmic conductor is DIRECTLY proportional to the PD across it
What are the conductors which obey ohms law called
Ohmic conductors (mostly metals)
What does the graph of an ohmic conductor show when you plot voltage against current
Straight line (origin) Double pd double current- directly proportional Resistance constant - gradient always fixed
What will have a significant effect on resistance (resistivity changes)
Light level
Temperature
What is internal resistance
Loss of pd per unit current
