Electricity Flashcards
Electric Charge
Indicate if a body has an excess or a deficiency of electrons
Electrostatics
The properties of charge particles at rest
Negative charge
When an object gains electrons.
Polythene when rubbed a dry cloth
Positive charge
When an object loses electrons
Perspex when rubbed with a dry cloth
Point discharge
Where ions in the air either strongly attracted or appelled from the tip of a charged conductor and move towards or away from it
Coulomb’s law
The force between two point charges is directly proportional to the product of the charges at inversely proportional to the square of the distances between them
Electric field
The region of space in which electric forces can be felt
Electric field line
The line along which a positive charge would move if placed in the electric field
Electric field strength
Add a points in the electric field it is the force experienced per unit charged placed at that point in the field
E = F/Q
Potential difference (V)
The work done in moving a charge of one coulomb from 1point to another
V = W/Q
Insulator
A substance through which electric charge cannot flow
Conductor
A substance through which electric charge can flow
Coulomb
Unit for electric charge. One coulomb of charge passes a particular point when a current of 1 A flows for 1 second
1 Volt
The potential difference between two points if one Joule of work is done in bringing one coulomb of charge from one point to the other
Capacitance
The ratio of charge to voltage in a conductor
C = Q / V
Emf
Electromotive Force. The voltage applied to a circuit
Capacitor
An electrical device capable of storing electric charge
Farad
A capacitor has a capacitance of 1 farad, if by placing a charge of 1 coulomb on it raises it potential by 1 volt
1 F = 1 C/V
Resistance
The ratio of voltage across an object to the current flowing through it
R=V/I
Resistor
A device that converts electrical potential energy to some other form
Resistivity
A constant associated with resistance of a body. Equal to the product of the resistance of the body and its cross-sectional area divided by its length
Potential at a point
The difference in the potential at a given point and potential of the earth (take it to be 0)
Current
The rate of flow of charge
I = Q/t
Ammeter
A device that measures current. Must be connected in series
Voltmeter
Advice that measures potential difference across a component must be connected in parallel or across the component
AC vs DC
DC always flows in one direction, AC constantly changes direction