1
Q
What is the electric current?
A
The electric current is the rate of flow of charge in the wire or component.
2
Q
What causes current?
A
Current is due to the passage of charged particles. These charged particles are called charge carriers.
3
Q
2 examples of charge carriers
A
- In metals, the charge carriers are conduction electrons. They move about inside the metal, repeatedly colliding with each other and the fixed metal ions.
- In comparison, when an electron is passed through a salt solution, the charge is carried in the ions, which are charged atoms or molecules.
4
Q
The unit of current is the ampere:
A
Which is defined in terms of the magnetic force between two parallel wires when they carry the same current.
5
Q
What is the convention for current.
A
From positive to negative.
7
Q
When is coulomb equal to charge flow?
A
A coloumb is equal to the charge flow in one second when the current is one ampere.
8
Q
In an insulator:
A
- Each electron is attatched to an atom so they cannot move away from the atom.
- When a voltage is applied across an insulator, no current passes through.
- This is because no electrons can move through the insulator.
9
Q
In a metallic conductor:
A
- Most electrons are attached to metals but some are delocalized
- The delocalized electrons are the charge carriers in the metal.
- When a voltage is applied across the metal.
- These conduction electrons are attracted to the positive terminal of the metal.
10
Q
In a semiconductor:
A
- The number of charge carriers increases with an increase of temperature.
- The resistance of a semiconductor therefore decreases as its temperature is raised.
- A pure semiconducting material is referred to as an intrinsic semiconductor because conduction is due to electrons that break free from the atoms of the semiconductor.
11
Q
QΔ Eq.
A
ΔQ = IΔT
12
Q
Current formula
A
I = ΔQ/Δt
13
Q
Current rules
A
- At any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction.
14
Q
Components in series
A
- The current entering a component is the same as the current leaving the component.
- The current passing through 2 or more components in series is the same through each component.
