Electrostatics Flashcards
what is electrostatics
the study of electrically charged particles
what happens when 2 substances are rubbed together
electrons are removed from one ,leaving it positively charged ,and placed on the other leaving it negatively charged.
how can you charge conductors
by making contact with another charged object or by inductions
how can you charge insulators
by friction
discuss static charges
only insulators can hold on static charges and on materials that are good insulators the charges leak away over a period of time.
A charged object can induce charges on other nearby charges .
What is the unit of charge for electrostatics
Coulomb (C)
what are the other variations of charge do we use
milli coulomb =1x10^-3C
Nano coulomb=1x10^-9C
micro coulomb =1x10^-6C
pico coulomb =1x10^-12C
what is the charge of a proton and electron
p+=1,6 x10^-19
e-= -1,6 x10^-19
The size of electrostatics charge ? how do we calculate charge?
Q=number of electrons(or protons)x1,6 x10^-19
what is the symbol used to represent the size of electrostatic charge
Q
state the law of conservation of charge
charge cannot be created nor destroyed but can move from one object to the other.
describe how charge can be shared equally amongst 2 objects(the formula )
add the charge of the different objects and divide by 2
discuss electrostatics force
electrostatics force occur between objects which are charged. Objects with like charges repel each other .Objects which have unlike charges attract each other. The force of attraction or repulsion depends on how much charge is on each of the 2 objects and how far apart they are .
state coulombs law
The force of attraction or repulsion between 2 charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between their centers.
what is the coulomb law’s constant
9 x10^9 N.m^2C^-2
elaborate on the calculation of the the force between 2 charged objects
F =KQ1Q2/r^2
F =is the electrostatic force in Newtons
Q1 and Q2 are charges on the objects in Coulombs
r is the distance between the centers of the objects in meters
k is the Coulombs law’s constant
discuss electric fields
we can picture the area around a charged object as a force field in which any other charged object will experience a force of attraction or repulsion. We represent an electric field by drawing field lines .
discuss the 4 points of electric fields
=Field lines are imaginary lines that indicate the direction and strength of an electric field at a point in the field.
= the direction of an electric field at a given point is the direction in which small POSITIVE test charge would move if placed at that point
=If the field lines are clos together this shows a strong field .
=Field lines never cross ,their direction is always from a positive towards a negative charge and they begin and end at right angles to the surface.
discuss electric field patterns
=they are around single point charges
=between 2 point charges
=between 2 parallel plates
elaborate on the electric field patterns points (1st)
=The field lines spread outwards from the point charge and form the radii of the circle. These are the radical fields. The strength of the field decreases as the distance from the point charge increases.
elaborate on the electric field patterns points (2nd)
=The fields of the 2 charges combine to give a resultant field. These fields are similar to the magnetic fields which you studies last year.
elaborate on the electric field patterns points (3rd)
When two metal plates are charged with opposite charges the electric field between them has the same strength strength at all points. The field lines run parallel to each other and we say that this is a uniform field.
If a small test charge is paced anywhere in this field, the force that it experiences will have the same magnitude
How do we measure electric field strength ?
At any point in an electric field the strength of the field is measure by the force exerted per unit positive charge placed at that point
hat is the formula for field strength
field strength=force/charge
E=F/q
electrostatic force formula?
F=qE
discuss field strength of a point charge
The pattern for the field around a point charge shows that the field strength of a point charge decreases as the distance from the charge increases. We can also see that the strength of the field will depend on the size of the charge which is creating the field.
discuss the field strength of a point charge formula
E=kQ/r^2
=E is the field strength (.C^-1)
=Q is the charge which creates the field (C)
=r is the distance from the charge (m)
=k is the Coulomb’s law constant=9 x10^9 N.m^2.C^-2
A shocking tail?? (fish)
A number of fish use electric fields for detection and communication. A charge separator in the body of the fish produces an electric field like that of a dipole. The strength of this field is monitored by receptors along the body of the fish. A conducting object near the fish will alter the strength of the field allowing the fish to “see” the object
A shocking tail?? (sharks)
Sharks also have electro-receptors that can pick up weak electric fields caused by small charges on an object. These electro-receptors are very sensitive and can detect field strengths as weak as 1 x10^-6N.C^-1.The electric field strength between the knee and shoulders of a swimmer is about 1000 times higher than this (i.e.. about 1 x10^-3N.C^-1).A shark can detect a swimmer at a distance of about 10m!
what is static charge /electricity?
What is meant by static charge?
Static electricity is a familiar electric phenomenon in which charged particles are transferred from one body to another. For example, if two objects are rubbed together, especially if the objects are insulators and the surrounding air is dry, the objects acquire equal and opposite charges
charge is quantised
The charge on an object will always be multiples of the unit charge of an electron
