Unit 2.1: Conduction of electricity Flashcards
What is the unit of charge?
Coulomb (C)
Particles can be___,_____ or____ charged.
neutral, negatively or positively
If an object is positively charged, has it lost or gained electrons?
It has lost electrons
If an object is negatively charged, has it lost or gained electrons?
It has gained electrons
What is the charge of an electron in Coulombs?
1.6x10^-19C
What is a conventional current?
When the current flows from positive to negative. This is due to conventions established a long time ago
What is electron flow?
When current flows from negative to positive
Define electric current
The rate of flow of charge or the flow of electrons in a circuit
State the equation associated with electrical current
I=ΔQ/Δt
I=Current
Q=total charge
t=time
On a current-time graph, what does the area under the graph give us?
The total charge,Q, because Q=It
State the equation used to transfer Coulombs into electrons.
Q (total charge) is equivelent to
Q/e where e is 1.6x10^-19C
1C=6.25x10^18 electrons
What is a free electron?
Outer electrons which are free to move around the lattice.
If no current is flowing through a metal, how will free electrons move and what is this called?
They will move randomly throughout the structure. This is called Thermal velocity
When a potential difference is applied across the ends of a metal an electric field is produced. What does this do to the free electrons?
The electric field exerts a force on the free
electrons, causing them to accelerate towards the highest potential (voltage).
Explain drift velocity
-p.d is applied, which creates electric field
- Free electrons accelerate towards positive p.d
-bouncing from atom to atom along the way.
State the relationship between the mean drift velocity and the applied electric field, and what this means in terms of current
The mean drift velocity is directly proportional to the applied field. Hence, the current we get is proportional to the applied voltage
Why do we have to supply energy to maintain current?
We have to give the electrons kinetic energy to move them along.
- Lose when colliding with metal ions
-As a result, electrical energy is turned into thermal energy.
State the equation associated with drift velocity
I=nAve
Derive I=nAve
Area=A
Volume of wire=A x l
Number of free electrons=nAl
Total charge= Q=nale
Distance moved=x=vt
So Q=navte
It=Q
It=nAvte
I=nAvte/t
I=nAve
What effect does doubling the drift velocity have on the current?
If the drift velocity doubles then the current also doubles.
