Further Electrical Concepts Flashcards
(38 cards)
Where does an electric field exist?
Around any point that has a negative or positive charge.
Likened to a gravitational field.
How can an electric field be visualised?
By lines pointing away from a positively charged point or lines pointing towards a negatively charged point.
Where can you find a magnetic field?
Exists around all magnets and around any conductor through which current is flowing.
Magnetic field has North and South Pole.
Where are the lines of force or flux of a magnetic field?
They run from north to south in curved lines round the outside of the magnet.
Magnetic lines of force will never cross.
What is the Lorentz force?
When a charged particle moves through a magnetic field, a force on the charged particle is produced, deflecting to movement through the field.
When is the Lorentz form at its maximum?
When the movement of charged particles is at a right angle to the direction of the magnetic field.
When is no Lorentz force exerted on a charged particle?
If it is moving in the same direction as the magnetic field.
What is capacitance?
The ability of a circuit to store an electric charge or electrical energy.
In other words, the amount of energy a capacitor can store for a given voltage.
What is a dielectric?
A thin insulating material which separates two conductive plates inside a capacitor.
What material is a dielectric?
Can be
Air
Paper
Or any other suitable material
What is a dielectric constant?
This is the dielectric value each material has when used as a dielectric.
It is a measure of its effectiveness when compared with that of a vacuum.
What value does a vacuum, air and paper have?
Vacuum has a value of 1
Air has a value slightly greater than 1
Paper has a value of 3.85
What is capacitance measured in?
Farads
What 3 factors determine capacitance?
The area of the plates (larger area - greater capacitance)
The distance between the plates (closer together - greater capacitance)
The dielectric constant of the dielectric (higher value - greater capacitance)
What are the different types of capacitors?
Simple air gap
Practical capacitor
Can capacitor (rolled plates)
What is the formula for capacitance?
C = q/v
C= capacitance in farads Q= charge V= voltage
What form of current runs through a dielectric?
No current flows as it is an insulator.
Current flow is from one plate through the supply to the other plate.
How quickly is a capacitor charged and discharged?
Charges quickly
Discharges equally quickly in the opposite directions when energy is released.
What are capacitors used to prevent?
Arcing across electrical junctions, such as contacts and relays
How are capacitors wired?
In series.
When wired in parallel to the junction, the capacitor provides an alternative path for current to flow.
What is voltage?
The electrical potential difference across two points in a circuit or across the terminals of a battery.
Measured in volts and given the letter V or E (emf).
What is voltage measured with?
A voltmeter which is wired in parallel with the circuit.
What is current?
The flow of electrons.
Is measured in amps or amperes.
Represented with letter I.
What is current measured with?
Ammeter which is connected within the circuit to measure the current through the circuit.
