Electric And Magnetic Fields Flashcards
What is capacitance
The ratio of the charge stored in a capacitor to the potential difference between the two sides of the capacitor
What is Coulomb’s law
The size of the force that acts between two point charges is proportional to the product of their charges and inversely proportional to the square of their separation.
F=k Q1Q2/ r^2
What is a dielectric
An insulating material placed between capacitors plates that prevents charge from crossing between the plates
It becomes polarised when the capacitor is charged and changes the capacitance of the capacitor
What is an eddy current
Small closed loops of current within a conductor or magnet
In a transformer these currents act against the magnetic flux that generates a current in the secondary coil making the transformer less efficient and heating the core
What is an electric field
A region of space in which charged partical experience either and attractive or repulsive force depending on the charge of the partial and direction of the field
What are electric field line and what doe they represent
Represent the electric field
The direction of the line is the direction of the field
Lines go from positive to negative
Closer lines are stronger the force is
Define electric field strength
The electrostatic force experienced by a small point positive charge at a particular point in the field
What is electric potential
The work done moving a unit positive charge from an infinite distance away to a particular point
Define electric potential difference
The work done moving a unit positive charge between two points in a field
Electromagnetic induction
When a current carrying conductor moves relative to a magnetic field an EMF is induced in the conductor
Flemings left hand rule
What is electrostatic force
The force generated between charges due to coulomb’s law
What does Equipotential mean
2 points in an electric field where the electric potential is the same
What is Faraday’s law
The magnitude of the inducedEMF is directly proportional to the rate of change os magnetic flux linkage
What conditions does flemings left hand rule need to work
What does each finger and thumb represent
The current and mag field need to be at 90 degrees to each other
Thumb - force
First finger - Field
SeCond finger - Current
What is frequency
The number of complete oscillations of the current in an A.C. Circuit per second
What does lamination mean
When a transformers core is made up of sets of layers to prevent eddy currents
What is Lenz’s Law
The direction of an induced current is such that it opposes the current that created it
What is a magnetic field
A region of space in which magnetic materials and moving electric charges fee a force
Wht is magnetic flux
The magnetic fild passing though a given area
The product of magnetic flux density and the area
What is magnetic flux dencity
The strength of a magnetic field measured in Tesla
What is magnetic flux linkage
The magnetic flux of a coil found by the product of the magnetic flux and number of turns of a coil
What is the motor effect
The force felt by a current carrying wire in a magnetic field
What is a period
The time taken for the current (or voltage) in an A.C. Circuit to complete one full cycle
What is a redial field
A field with field line originating from one point
