There are two types of charges, positive and negative charges
Unlike charges attract and like charges repel
Adding a charge to something involves the addition or removal of electrons
Current is related to the flow of charge
Current in metals is due to a flow of electrons
The potentialdifference across a circuit component is measured in volts
The electromotiveforce of an electrical source of energy is measured in volts
V=IR
PotentialDifference = Current multiplied by Resistance
For a parallel circuit, the current from the source is larger than the current in eachbranch
The combined resistance of two resistors in parallel is less than that of either resistor by itself
The current from the source is the sum of the currents in the separatebranches of a parallel circuit
The sum of the potentialdifferences across the components in a series circuit is equal to the totalpotentialdifference across the supply
Electric charge is measured in units called coulombs
An ammeter measures the current in a circuit and is connected in series
Conventionalcurrent flows in the direction opposite to that which electrons flow in.
Red = Conventional Current
Green = flow of electrons
The energy supplied by the source in driving a unit charge around a circuit.
The maximum voltage a cell can produce is called the electromotive force (EMF), measured in volts.
The current at any point in a series circuit is the same
The current splits at each branch in a parallel circuit so the total current is always greater than the current in one branch
In parallel: Current across the source = sum of currents in the separate branches
Electrostatic repulsion is caused by the force between charges. When the charges are the same, they repel each other.
In experiments showing the production of electrostatic charges by friction, insulating solids like plastics are given a charge. This is done using friction to transfer electrons from the surface. By removing negative electrons, the insulator is left with a positive charge.
A charged object creates an electricfield around itself. This can be shown by electricfieldlines.
Electric field lines always point away from positive charges and towards negative charges
A) +
B) -
The strength of an electric field depends on the distance from the object creating the field:
The field is strongest closeto the charged object - this is shown by the fieldlines being closertogether
The field becomes weaker furtheraway from the charged object - this is shown by the fieldlines becoming furtherapart
Objects in an electric field will experience an electrostaticforce
The force of an electrostatic force is either attractive or repulsive depending on whether the charges are opposite (positive and negative) or the same (positive and positive)
Fields lines always go away from positive charges and towards negative charges – they have the same direction as the direction of the force on a positively charged particle at a point in that field
The electric field between two parallel plates is a uniform electric field.
The field lines are:
Directed from the positive to the negative plate
Parallel
Straight lines
Conductors allow charge carriers to freely move
Insulators do not allow charge carriers to move
A conductor is a material that allows charge (usually electrons) to flow through it easily
Examples of conductors are:
Silver
copper
Aluminium
Steel
Conductors tend to be metals
An insulator is a material that has nofreecharges, hence does not allow the flow of charge through them very easily
Examples of insulators are:
Rubber
Plastic
Glass
Wood
The current is the amount of charge passing a point in a circuit every second
Q = I × t
Charge = Current × Time
Charge is measured in coulombs
Current is measured in amps
The electromotive Force (e.m.f.) is the name given to the potential difference of the powersource in a circuit
The EMF of a circuit is defined as The electricalworkdone by a source in moving a unit charge around a completecircuit