Physics - Recall for Chapter 8: Current and Charge
OCR A-Level Physics 2022
Recall Questions
Current and charge
Define the coulomb?
The SI unit of electrical charge. One Coulomb is defined as the amount of charge that passes in 1 second when the current is 1 ampere.
What do we mean when we say charge is quantised?
It can only take certain values (always $ne$).
If $n$ electrons are removed from a neutral object, what is its charge?
Conductors and current carriers
What is a metallic conductor?
A material comprising a lattice of positive ions and delocalised electrons that carry electrical current.
Which direction does conventional current flow in a circuit?
From positive to negative.
Ammeters and Kirchhoff’s first law
What is the resistance of an ideal ammeter?
$0$ - Ammeters have very small resistance so they have a negligible potential difference across them.
State Kirchhoff’s first law (long)?
At any point in a circuit, the sum of the currents entering that point is equal to the sum of the currents leaving.
What is Kirchhoff’s first law an example of the conservation of?
Charge.
The equation I = nAve
Conductors, insulators and semiconductors
What is a semiconductor?
A material with an intermediate number density of charge carriers.