Chapter 8 Flashcards
Charge and Current
What is the SI units for electric current
Amperes(A)
What is electric current defined as?
Electric current is defined as the rate of flow of charge
What is the equation linking
- Current
- Charge
- Time
Q = I x t
What is the SI unit for charge
Coulombs
What is current derived from the equation Q = It
The amount of charge passing a given point in circuit per unit time
What is 1A equal to
1 C/s
What type of property is electric charge
A physical property
What are the 2 types of charges
1) Positive
2) Negative
What are ions described as when they referred by their charges
Relative charges
What is e
Elementary Charge
What is Elementary Charge
The relative charge a proton has e
(A electron has a charge of
-e)
What is the value of e
1.60 x 10^-19C
What is net charge
the charge on the object which is due to its gain or loss of electrons
How do you calculate the net charge on a object
Q = ne
Q-Coulombs
n-Number of electrons
e-Elementary charge
What is a charge carrier
carriers of charge(lol)
Name 2 charge carriers and where they operate
Electrons - Metals
Ions - Liquids
What is one way to make electrons to move in a metal wire
to make a positive end- this means all the electrons will flow towards to this direction
The greater the the rate of charge flow
the greater the electric current in a wire
What may a large current be due to?
1) A greater number of electrons moving past a given point each second
(e. g. a wire with a greater cross-sectional area)
2)A increase in the speed of the electrons moving faster through the metal
What is Conventional current
The direction of the electric current from the positive terminal to negative terminal
What is electron flow
The direction of the electric current from the negative terminal to the positive terminal
What is the name of the liquids that can carry current
Electrolyte
What are all the electrolyte
Molten ionic compounds
or
Ionic solution
What is the positive and negative electrodes called
1) Cathode(-)
2) Anode(+)
What is an ammeter used for
To measure the electric current at any point in a circuit
How much resistance does an ammeter have
Very little resistance
so it does not affect the current
Is the ammeter in parallel or in series
series
What does the conservation of charge state
That electric charge cannot be created nor destroyed
What does Kirchhoff’s first law states
For any point in an electrical circuit, the sum of currents into that points is equal to the sum of currents out of the circuit
What is number density
It is the number of free electrons per cubic metre of material.
What does a higher number density mean
The greater the number density the better the electrical current
What are the 3 types of number density classification
1) Insulators
2) Semi-conductors
3) Conductors
What is the value of number density for conductors
Y x 10^28m-3
What is the value of number density for semi-conductors
Y x 10^17m-3
Why does appliances turn on instantly
This due to all the free electrons in the wire moving almost instantly
What is the equation linking
- Current
- Mean drift velocity
- Elementary Charge
- Number of electrons
- Cross sectional area
I = A x n x e x v
What is mean drift velocity
The average velocity gained by the free electrons of a conductor, with which the electrons get drifted under the influence of an electric field
What affect does the Cross sectional area of a wire have in the drift velocity
the smaller the Cross sectional area the higher the mean drift velocity
