Charge and current Flashcards
Unit of current
Ampere(A)
What is current
Rate of flow of charge
Unit of charge
Coulomb
Base unit of charge
Ampere second (A s)
What is elementary charge
The electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 e. 1e = 1.6 x 10E-19
Net charge on most object must be a multiple of e. Why?
Because charges on most object results form either gaining or losing electron. An electron has charges of -1 elementary charges and it can’t be broken into smaller pieces, so charge always changes in multiples of the elementary charge.
We describe the charge on an object as being quantised . Why?
Because charge can only have a certain values (multiple of e).
In metal the charge carriers are electrons, but on liquid the charge carriers tend to be ______
Ions
A larger current may be due to ___ or _____
A greater number of electron moving past a given point each second (Greater cross section area)
The same number of electron moving faster
Conventional current flow from ___ to ____
Positive to negative
The conventional current’s direction is actually wrong. Why?
Conventional current is defined before the discovery of electron. Electron actually move from negative to positive
Liquids that can carry an electric current are called ___
Electrolytes
State Kirchhoff’s first law
For any point in an electrical circuit, the sum of current into that pint is equal to the sum of current out of that point.
Explain why Kirchhoff’s first law work
The law is based on conservation of charge. And charge is a product of current. As charge cannot be destroy, the charge carriers in must equal to the charge carrier out.
What is number density in the context of electricity
It is the number of free electron per unit volume
