Electricity Flashcards
(17 cards)
Define current
The rate of flow of charge
How can current be measured?
Use an ammeter in series
How is current carried in a metal?
Electrons
How is current carried in an electrolyte?
Ions
What direction is conventional current?
Positive to negative
What direction is electron flow?
Negative to positive
What is Kirchhoff’s first law?
For any point in an electrical circuit, the sum of the currents in to that point is equal to the sum of the currents coming out of that point
What gets conserved due to Kirchhoff’s first law?
Charge
What is the mean drift velocity?
The average velocity of the electrons as they travel down the wire, colliding with positive metal ions
What is number density?
The number of free electrons per unit volume
What is potential difference?
The work done by charge carriers, as they pass through components
What is emf?
The work done to charge carriers, as they pass through a power supply
What is Ohm’s law?
For a metallic conductor kept at a constant temperature, the current in the wire is directly proportional to the potential difference across it
What is Kirchhoff’s second law?
In any circuit the sum of the electromotive force is equal to the sum of the potential difference in a closed loop
What gets conserved due to Kirchhoff’s second law?
Energy
What is the pd lost across the power supply called?
Lost volts
How does an electron gun work?
An electron gun is a device used to produce a thin beam of electrons, which are accelerated to high speeds. A small metal filament, which acts as a cathode, is heated by passing a potential difference through it. Some of the electrons in the metal gain enough kinetic energy to escape the metal, in a process known as thermionic emission. The circuit is in a vacuum tube, with a high p.d., V, between the filament and the anode, so the freed electrons are accelerated towards the anode. If the anode has a small hole in it, a beam of electrons can pass through at a specific kinetic energy.
