P6: Static, Current Electricity and Circuits Flashcards
Tool to remember circuit calculations
- Draw 5 triangles in the order shown in the diagram
- place one unit symbol at each vertex of each triangle and between the vertices of adjacent triangles starting from the left and in an up-down pattern.
- The symbols to be selected are taken from the nemonic:
Can Julie Visit W***_atson _***A***_nd _***C***_arry _***S***_ome _***Jellybeans With A***_ssorted _***Raisins?
Each triangle represents a triangle formula
true or false: Neutral bodies have the same number of negative and positive charges
- true
true or false: in metals both electrons and protons can be mobile
false: the positive charges remain fixed
true or false: electron flow in the same direction of conventional current flow
false: the flow is opposite
true or false: all matter contains positive and negative charges
true
true or false: the positive and negative charges in a liquid can be mobile
true
define electrostatic induction
process by which electrical properties are transferred from one body to another without physical contact
in terms of electrostatics, what happens if a glass rod is rubbed with a piece of cloth
electrons transfer from the glass rod to the cloth resulting in a positively charged glass rod and negatively charged piece of cloth
in terms of electrostatics, what happens if a polythene(plastic) rod is rubbed with a piece of cloth
electrons transfer from the cloth to the polyethene rod resulting in a positively charged cloth and negatively charged of rod
true or false: an charged body can attract an uncharged one
true.
what subatomic particle is used to explain electrostatics
the electron
a charged polythene rod is brought near a small piece of uncharged paper and the paper sticks to the rod. Explain what may have happened
the polythene rode is negatively charged and the electrons on its surface repel the electrons on the surface of the paper, leaving a net positive charge which is now attracted to the negative charge on the rod
what are some useful applications of static charge
- lightening conductors to protect buidings
- use in electrostatic dust precipitators to reduce pollution of the environment from dust and carbon particles contained in smoke
- electrospraying of objects such a motorvehicles
- photocopiers
how is electric current carried in metals and graphite?
by electrons
how is electric current carried in a molten metallic compound?
ions
Electrical field from negative charge
what idealized model is used to study electric fields?
the positive test particle
Electrical field form positive charge
- what charge does this particle possess?
- where is the electric field strongest?
- its positively charged because the electric field goes outward from the particle
- the electric field is strongest nearest to the particle because the field lines are closest together near the particle
two charged plates A and B are placed near each other.
- what is the charge on plate A
- what is the charge on plate B
- plate A is positive
- plate B is negative
- what charge does this particle possess?
- where is the electric field strongest?
- its negatively charged because the electric field goes toward the particle
- the electric field is strongest nearest to the particle because the field lines are closest together near the particle
two particles A and B are in an electric field
- what is the charge of paricle A
- What is the charge of particle B
- where is the field strongest between the particles?
- Where is the weakest field between the two particles?
- charge on particle A is negative
- charge on particle B is positive
- electric field between them is strongest at C.
- the weakest electric field between them is at D
two charged particles A and B arein an electric field
- what is the charge of paricle A
- What is the charge of particle B
- Describe the electric field at C
- charge on particle A is negative
- charge on particle B is negative
- no electric field at C as the resultant electric force is 0
two charged particles A and B are in an electric field
- what is the charge of paricle A
- What is the charge of particle B
- Describe the electric field at C
- charge on particle A is positive
- charge on particle B is positive
- no electric field at C as the resultant electric force is 0
how is electricity charge carried in ionic solutions ie solutions of salts
ions
what is electric current?
electric current is the rate of flow of electric charge
what is the equation to calculate elecric current
I = Q/t
Q is electric charge
t is time the the charge flows for.
what is the unit of current?
Amperes(A)
what is the unit of electric charge?
Coulomb(C)
What is the definition of the Coulomb
The unit of electric charge
what is the equation for calculating the amount of electric charge?
Q = I x t
- Q is charge*
- I is electric current*
- t is time*
what is the Faraday constant?
The charge on 1 mole of electrons which is equal to 96500 C/mol
what is an electric field?
an electric field is the region in which a body experiences a force due to its charge
what is the difference between electron flow and conventional current
electron flow is movement of negative charge conventional current is the direction in which a positive charge would move if it were free to do so. It is the direction of the electric field
what is the direction of an electric field?
The direction of the field is taken to be the direction of the force it would exert on a positive test particle. The electric field direction about a positive test particle is always directed away from the positive source.
what is alternating current?
Alternating current describes the flow of charge that changes direction periodically.
what is direct current?
the flow of charge in only one direction.
what is frequency of the a/c source?
number of oscillations or cycles per second. unit is Hz(Herts)
in electricity calculations it is determined by :
f = 1/T
what is Periofd (T)
time taken to complete one oscillation
T = 1/f
sources of A/C current
electric generators
sources of direct current
cells and batteries
what is rectification?
the process of converting a/c current to d/c current.
types of rectification
- half wave and
- full wave rectification
what electrical component carries out rectification and how?
a diode carries out rectification and does it by only allowing the electric current to flow in one direction
what is a capacitor
a simple device that stores electric charge for a short period of time
what is a semiconductor?
material with conductivity between that of a conductor and an insulator
main substance used as a semiconductor
silicon
important function of a semi conductor such as silicon
used to make many components of electric circuits
What does potential difference(pd) across a conductor mean?
the potential difference between two points in a circuit is the energy used (or work done) in transferring a unit charge between those 2 points.
what is electromotive force(emf) of a cell?
The emf of a cell is the energy used(or work done) in transferring a unit charge around a complete circuit, including the cell itself
what is the unit of pd and emf
The volt, V
when is emf used?
when referring to the pd in a cell or battery
what is the equation for emf and pd
V=E/Q
- V is voltage
- E is electrical potential energy
- Q is electrical charge