P5 - Electricity Flashcards
What is current?
The rate of flow of charge
What is potential difference?
The energy transferred between two points in a circuit
What is resistance?
A measure of the opposition of a component to the flow of charge
What is Ohm’s law?
For an ohmic conductor, current is directly proportional to the potential difference if the temperature is kept constant.
How much resistance do ammeters have?
0
How much resistance do voltmeters have?
Infinite
What is resistivity?
A measure of how easily a material conducts electricity.
What happens to the resistance of a metal conductor as its temperature increases?
Its resistance will increase
What happens to the resistance of a thermistor as its temperature increases?
Its resistance will decrease
What is a super conductor?
A material which has 0 resistivity below a certain temperature (critical temperature)
What can superconductors be used for?
Power cables to reduce energy loss through heating.
What is power?
Energy transferred over time
I-V in series:
- Current is the same everywhere.
- Voltage is added to get the total
I-V in parallel:
- Current is added to get total
- Voltage is the same across each branch
When identical cells are joined in parallel…
The voltage is equal to that of one cell
What is Kirchoff’s first law?
Current is the same before and after the component
What is Kirchoff’s second law?
(In series) Vtot = V1 + V2 + V3….
What is the electromotive force?
Energy transferred by a cell per coulomb of charge that passes through it
What causes internal resistance?
Electrons within the battery colliding with atoms, causing energy to be lost before electrons even leave the battery
What is EMF the product of?
emf = I(R+r)
