What is current?
-Rate of flow of charge
How can you calculate current using time?
What is ΔQ measured in?
-Coulombs (unit of charge)
Define 1 Coulomb
-Amount of charge that passes in 1 second when the current is 1 ampere
How can you measure current flowing through a circuit?
Where does an ammeter need to be attached in a circuit? Why?
-Current through ammeter is the same as current through the component
Define potential difference
-Energy converted per unit charge moved
What needs to be done to electric charge to make it flow through a conductor?
-Work must be done on it
How can you work out voltage using charge?
What is ‘W’ in order to work out potential difference?
-Energy in joules, work done to move the charge
Define a volt
-Potential difference across a component is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component
Finish this equation in terms of the definition of potential difference.
-1V = 1JC-1
What does current for a particular potential difference depend on?
-Resistance of component
How do you calculate resistance using voltage?
What is resistance measured in?
A component has a resistance of 1 Ω if a potential difference of 1 V makes a current of *A flow through it
For what sort of conductor is resistance a constant?
What sorts of conductors obey Ohm’s law?
Name 2 factors that are directly proportional in an Ohmic conductor. What must remain constant?
-Current and potential difference
How will factors such as light level or temperature have significant effects on resistance?
Finish this sentence: “Ohm’s law is a special case; it is only true for…
-Ohmic conductors at constant temperature
What do I/V graphs/characteristics show?
-How resistance varies
What does the gradient of an I/V graph show?
-Resistance. Shallower the gradient of a characteristic I/V graph, the greater the resistance of the component
What is the I/V characteristic for a metallic conductor?
-Straight line through zero (0)
Which I/V characteristic is a curve through zero (0)?
-I/V characteristic for a filament lamp
Why doesn’t a filament lamp have the same (straight line) characteristic of a metallic conductor?
-Gets hot. Current flowing through lamp increases its temperature
The ********** of a metal increases as the temperature increases
Where are semiconductors used?
-Nowhere near as good at conducting as metals, due to few charge carriers. If energy is supplied to semi-conductor, more charge carriers can be released. Meaning they make excellent sensors for detecting changes in their environment
Which 3 semiconductor components do you need to know about?
-Thermistors, LDRs (Light Dependent Resistors), Diodes
What does resistance of…