Chapter 12 - Electricity Flashcards
(22 cards)
What is a charge carrier?
A charged particle e.g.electron
What is an insulator?
No current passes through the substance
What is a metallic conductor?
It has delocalised electrons so can carry charge
What is a semi-conductor?
The number of charge carriers increases with an increase in temperature, so it does conduct electricity, but it conducts more as the heat increases
What is potential difference?
The work done per unit of charge
What is the emf?
The electrical energy produced per unit charge passing through the source
What is Ohms law?
The pd across a metallic conductor is proportional to the current through it, provided the physical conditions don’t change
What happens to the current in a series circuit?
It’s the same all the way around the circuit
What happens to the potential difference in a series circuit?
It is shared amongst components
What happens to the current in a parallel circuit?
It’s shared between branches
What happens to the potential difference in a parallel circuit?
Each branch will have the same pd as the power source
What is current?
The rate of flow of charge
What is resistance?
Opposition to the current in a substance
What is electrical power?
The rate, per unit time, at which electrical energy is transferred by an electric current
What causes resistance?
Collisions between electrons (what flow in current) and ions (the nuclei left over after the electrons have delocalised)
What is resistivity?
Resistance per unit length x area of cross section
What is a super conductor?
A material that has zero electrical resistance
What is the critical temperature?
The temperature at which a super conducting material’s resistivity is zero
Uses of super conductors
Strong electromagnets, power cables and electronic circuits
What happens to the current in a filament bulb when you keep upping the pd?
At low pd values they are pretty much directly proportional, however as the pd increases, the resistance increases - this means that there is less current at a higher pd. This is because the bulb has gotten hot and so the particles vibrate more and so the lattice vibrates, so there are more collisions with charge carriers (the resistance increases)
What happens to the current when you up the pd in a diode?
The current stays at zero until 0.6V when the current starts increasing rapidly
What happens to the resistance in a thermistor as the temperature increases?
As the temperature increases the resistance decreases, as more charge carriers are freed and therefore more current can flow
