1. Charge + Current

What does current mean + equation?

• Current - rate of flow of charge (A)

• Q = It (charge = current x time)

What is the elementary charge?

e = 1.6 × 10^-19 C

What are the charge carriers in metals + electrolytes?

• Metals → electrons

• Electrolytes → ions

What is conventional current + electron flow?

• Conventional current - current flows from positive to negative

• Electron flow - electrons flow from negative to positive (attracted to the positive terminal because they are negatively charged)

What is Kirchhoff’s first law?

The sum of currents entering a junction = the sum of the currents leaving the junction (e.g in parallel circuits the current splits at the junction)

Why does Kirchhoff’s first law exist?

Due to the conservation of charge

What is the mean drift velocity equation?

I = nAve

Current = free charge carrier density x cross-sectional area x mean drift velocity x elementary charge

What does mean drift velocity mean?

The average velocity of charge carriers as they travel down a conductor (e.g whilst electrons collide with positive ions)

What is the difference between conductor, semi-conductors + insulators?

• Conductor → high n value (e.g x10²⁸)

• Semi-conductor → medium n value (e.g x10¹⁶)

• Insulator → low n value (e.g x10⁵)