Current and Charge

Question 1

What is the electric current?

Answer 1

The electric current is the rate of flow of charge in the wire or component.

Question 2

What causes current?

Answer 2

Current is due to the passage of charged particles. These charged particles are called charge carriers.

Question 3

2 examples of charge carriers

Answer 3

• 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.

Question 4

The unit of current is the ampere:

Answer 4

Which is defined in terms of the magnetic force between two parallel wires when they carry the same current.

Question 5

What is the convention for current.

Answer 5

From positive to negative.

Question 7

When is coulomb equal to charge flow?

Answer 7

A coloumb is equal to the charge flow in one second when the current is one ampere.

Question 8

In an insulator:

Answer 8

• 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.

Question 9

In a metallic conductor:

Answer 9

• 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.

Question 10

In a semiconductor:

Answer 10

• 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.

Question 11

QΔ Eq.

Answer 11

ΔQ = IΔT

Question 12

Current formula

Answer 12

I = ΔQ/Δt

Question 13

Current rules

Answer 13

• At any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction.

Question 14

Components in series

Answer 14

• 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.