Electrostatics Flashcards
What are the two types of charge
Positive charges namely protons and negative charges namely electrons.
What Is tribo electrical charge
The process by which electrons are transferred when two objects come Into contact with each other and are then separated from each other. During the process of tribo electrical charge, one object wins electrons on its surface and is charged negatively, the other object loses electrons from its surface and is positively charged
What does the word tribo mean
To rub
What is the tribo electrical series
The tendency of a substance to either give up electrons and be positively charged or take up electrons and be negatively charged
What are the substances on the tribo electrical series
Dry skin human Rabbit fur Perspex Cellulose acetate Glass Human hair Nylon Wool Cat hair Flannel Silk Paper Cotton (neutral) Steel (neutral) Wood (neutral) Ebony Rubber ballon Stiff rubber Nickel, copper, silver Foam plastic Cling plastic Polythene Polyethylene (scotch tape) Vinyl (PVC) Silicone
What are the factors that influence electrostatic forces
Distance and magnitude of the charges
What is an electrostatic force
À force of attraction or répulsion between two charged objects
What is electrostatics
The study of charges at rest
What does matter consist of
Atoms or molecules which contain equal numbers of protons and electronS
How can insulators be charged
Through friction
How do positive ions form
Through the loss of electrons
How do negative ions form
Through the gaining of electrons
What will like charges do
Repel
What will unlike charges do
Attract
What is the law of conservation of electrical charge
Charges cannot be created or destroyed, but separated and transferred from one object to another. Therefore we say that the net charge of an isolated system remains constant
What is the unit of charge
Coulomb (C)
What is the elementary charge
The charge of an electron
What is the charge of an electron
-1,6 x 10^-19
What is the charge of a proton
1.6 x 10^-19
How do charges objects attract uncharged insulators (since their electrons cannot move freely)
a charged object attracts or repels an uncharged object to form a slightly negative pole and slightly positive pole on an object due to the movement of electrons from one side of the atoms in the object to another (to shield positive charges or unshield the positive charges. This is called a temporary dipole. Because this process takes place due to the proximity of an external charge we call this induced polarisation
How do charged objects attract uncharged conductors
A charged object repels or attracts the electrons of the conductor leaving an excess positive charge or excess negative charge which is then attracted by the charged object
What is a permanent dipole
When the arrangement of electrons in a molecule is uneven resulting in a slightly positive and slightly negative side even though the molecule as a whole is still neutral
Why are objects that are charged mounted onto an isolated stand during an experiment
So that the charges on the object do not become grounded
What is the symbol for electrical charge
Q or q
What is the equation for the charge when 2 identical size conductors come into contact
qnew = (q1 +q2)/2
What is the formula to determine the charges transferred
(Delta)q=qf-qi
What is the principle of quantisation
The observed charge on an isolated particle is always an integer multiple of e(1,6 x 10^-19)
What is Coulomb’s law
Two point charges in free space or air exert forces on each other. The force is directly proportional to the product of the charges and inversely proportional to the square of their distance between the charges
What is an electric field
A region of space in which an electric charge experienced a force. The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point
Define electric field strength
The force per unit positive charge
How can we determine if there is an electric field in a certain area
Place a test charge in the area. If the charge experienced a force, there is an electrical field in the area.
Learn the internet electric field lines on page 241
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What is an electric field line
An imaginary line that indicates the direction and strength along which a positive test charge will move if it is placed at a specific point in the electric field
What are the properties of electric field lines
- They originate and end perpendicularly to the surface of the charged object.
- They can never cross or touch each other.
- they are most dense (closer to each other) where the field is the strongest and are least dense (further from each other) where the field is the weakest.
- Their direction is, according to convention, from the positively charged object to the negatively charged object. -They surround the charged object in three dimensions. We only draw a few lines on one plane.
-There is a uniform field between two oppositely charged parallel plates (except at the terminal points).
How is the electric field between parallel charged plates
There is a uniform electrical field between the two oppositely charged parallel plates. A positive test charge will experience the same electrostatic force at any point in an electrical field between two positively charged parallel plates
How is the electric field around point charges and charged spheres
The electric field around point charges and charged spheres are not uniform. The further you move away from the charge or sphere, the weaker the electric field as well as the electrostatic force becomes
How is the electrical field around an irregular object
For objects that have an irregular shape the greatest charge is found at the sharpest areas where the electrical field is also the densest.
