Charge, Current and Potential Difference

Current equation

I = ΔQ/Δt

Current

The rate of flow of charge

Current symbol

I

Charge symbol

Q

What is current measured in

amperes

Ampere abbreviation

A

What is charge measured in

Coulombs

Coulombs abbreviation

C

1 coulomb

The amount of charge that passes in 1 second when the current is 1 ampere

Potential difference

Work done per unit charge moved

Potential difference equation

V = W/Q

1 volt

When you do 1 joule of work moving 1 coulomb of charge through the component

Charge carrier

Charged particles that are flowing

Examples of charge carriers

-Positive ions

-Negative ions

-Electrons

Type of charge carrier in an electric circuit

Electrons

Conduction electron

Electrons that are free to flow in a circuit

Conventional current

Flow of charge carriers from positive to negative

Electric current

Flow of charge carriers from negative to positive

What charge carriers follow conventional current

Positive ions

Which charge carriers follow electric current

-Negative ions

-Electrons

Conventional current of positive charge carriers is equal to what

Electric current of negative charge carriers, but in the opposite direction

Explain how a spark in a gas is created

When a high enough voltage is applied to a gas, the electrons are ripped out, giving ions along a path

How does current move through wire

Electrons move randomly in all directions, but tend to drift one way

Mean drift velocity

The average velocity of electrons in the direction they are drifting

Explain why mean drift velocity is much less than electrons’ actual speed

Electrons do not just move in one direction uniformly, they move randomly, but drift in one direction

Alternative current equation

I = nqvA

What does the n symbol represent in the alternative current equation

Number density of charge carriers

What is number density of charge carriers measured in

m^-3

What does the q symbol represent in the alternative current equation

Charge on each charge carrier

What does the v symbol represent in the alternative current equation

Mean drift velocity

What does the A symbol represent in the alternative current equation

Cross-sectional area

What does number density of charge carriers mean

The number of charge carriers per unit volume

Number density of charge carriers in a metal

High

Number density of charge carriers in a semiconductor

Less

Number density of charge carriers in an insulator

Very small

Number density of charge carriers in a perfect insulator

None