Charge and current Flashcards
What is electric current?
A flow of charged particles.
What is the equation for Q?
Q = I*change in t
What is electric charge?
A fundamental physical property that will cause objects to repel or attract one another.
Can charge have any value?
No, can only take certain values. Q=+-ne
How does current flow in metals?
Regular crystal/lattice structure of positive ions surrounded by a small number of delocalised electrons. The delocalised electrons move while the positive ions remained fixed in their positions.
How do you increase current in a wire?
Increase cross-sectional area or increase the speed of the electrons.
What is conventional current?
The flow of electrons from the positive terminal to the negative terminal.
How is electric current modelled in electrolytes?
Cations (+ve) are attracted to the cathode (-ve) and anions (-ve) are attracted to the anode (+ve). Electrons are donated and given so that they can flow through the metal part of the circuit.
What is Kirchhoff’s first law?
For any point in an electrical circuit, the sum of currents into that point is equal to the sum of currents out of that point.
Why do lights turn on so quickly?
Free electrons start moving all at once and they repeatedly collide with the positive ions.
Mean drift velocity equation:
v=I/Ane
How does decreasing the A of the wire change the drift velocity of the current?
Increases.
Explain mean drift velocity
- Free electrons make collisions with the metal ions and give them a random velocity
- The free electrons drift towards the positive end of the supply along the length of the wire
- The distance travelled per unit time along the length of the wire is called the mean drift velocity of the electrons
What is mean drift velocity?
- The avg distance travelled by the electrons per unit time along the length of the wire
- The direction of the electron flow towards the positive end of the external supply
