4.1 Charge and Current Flashcards
What is electric current? (3)
The rate of flow of charge
The movement of electrons in metals
The movement of ions in electrolytes
What is a coulomb? (2)
A unit of charge
1 amp = 1 coulomb per second
What is elementary charge?
1.6x10^-19 C
What is conventional current?
Flows from positive to negative
What is individual electron movement like?
Electrons move randomly but all drift in the same direction
What effect does adding components in series have on current?
Current decreases
What effect does adding components in parallel have on current?
Current increases
What is Kirchoff’s first law?
The sum of the currents into a junction is equal to the sum of currents leaving the junction
What does Kirchoff’s first law conserve?
Charge
What is mean drift velocity?
The average distance an electron moves along a wire in a given direction in one second
How is number density calculated?
n = I / Ave
n = number density (free electrons per m^3) (m^3) I = current (A) A = cross sectional area (m^2) v = drift velocity of charge carriers (ms^-1) e = charge on charge carrier (C)
What is number density?
The number of charge carriers per unit volume within a material, determining how well it conducts electricity
What is the number density of an insulator like?
The outer electrons in the atom form bonds that hold the material together so they aren’t free to conduct electricity
What is the number density of of a conductor like? (2)
Each atom within the lattice supplies at least one freely moving electron in order to form the bond holding the positive ions together, therefore conducting electricity
Electron drift velocity = mms^-1
What is the number density of a semiconductor like? (2)
Similarly to metals, there are some free electrons in semiconductors but fewer than in metals
The drift velocity is much higher in order to transfer the same amount of current with fewer electrons = ms^-1
