4.1 - Charge and current

What is electric current?

The rate of flow of charge, measured in Amps.

Give the symbol equation relating charge, current and time?

I=Q/t

Give 2 examples of possible charge carriers?

Electrons - in metals, Ions - in electrolytes

True or false: Current flows from negative to positive

False. Conventional current is the 'flow of positive charge' - it is in the opposite direction to the movement of the electrons in the circuit

How can you measure the current in a circuit?

With an ammeter connected in series with the component

What is Kirchhoff's first law?

The total current entering a junction = the total current leaving it

What is meant by 'mean drift velocity'?

The average velocity of the charge carriers due to the applied electric field. It has to be an average because they're often moving randomly in all directions.

What is the equation for mean drift velocity?

I = Anev, where I = current, A = cross sectional area , n = number density of charge carriers, e = charge of an electron and v = velocity

Put conductors, semi-conductors and insulators in order from highest 'n' (number density of charge carriers) to lowest

Highest: conductors

Semi-conductors

Lowest: insulators