Static electricity
● Protons and neutron are collectively called nucleons
● Types of charges
○ Positive +
○ Negative -
● Opposite charges attract each other while same charges repel each other
● Law of charges
○ Like charges repel each other
○ Unlike charges attract each other
● An object is grounded when connected to the earth through a connecting wire
● Object loses all its charge
● Symbol for grounding - ⏚
● Methods of charging a body
○ Friction
○ Conduction
○ Induction
● Charging by friction
○ When insulators are rubbed together, one gives up electrons and becomes positive
charged while the other gains electrons and becomes negatively charged
○ E.g the laundry from the dryer that sticks together
● Materials that gain a positive charge
○ Dry human skin
○ Leather
○ Human hair, cat fur
○ Nylon
○ Glass
○ Wool
○ Lead
● Materials that gain a negative charge
○ Wood
○ Nickel, copper
○ Gold, platinum
○ Polyethylene
● Materials neutral in nature
○ Cotton
○ Steel
● Charging by conduction
○ When a charged conductor makes contact with a neutral conductor there is a transfer of
charge
○ Electrons are transferred by the rod to the ball leaving them both negatively charged
○ It is the process where the charged particle is held near an unchanged conductive
material that is grounded on a neutrally charged material. The charge flows between 2
objects and the unchanged conductive material develops a charge with opposite polarity
● Charging by induction
● When the neutral metal
sphere meets the negatively charged rod, the charges separate and opposite charges attract,
the electrons or negative charged gets removed through grounding it and therefore we are left
with a positively charged metal sphere
● Electrical field
○ The region around the electric charge in which the stress or electric force acts is called
an electric field or electrostatic field
○ Electric field symbol is E
○ SI unit of is newton per coulomb (n/c) or volt/meter
○ If the magnetic field is large then it may create a huge stress around it ‘
Types of electric field
● Uniform electric field
○ When the electric field is constant at every point, it is a uniform
electric field
○ The constant field is obtained by placing 2 conductors parallel
to each other
● Non-uniform electric field
○ The field which is irregular at every point is called a non-
uniform electric field. The non-uniform field has a different
magnitude and direction.
● Properties of electric field lines
○ Field lines never intersect each other
○ They are perpendicular to the surface charge
○ The field is strong when the lines are close together and it is weak when they move
apart
○ The number of field lines is directly proportional to the magnitude of the charge
○ The electric field line starts from the positive charge to the negative charge
○ If the charge is single then they start and end at infinity
○ The curves are continuous in a charge-free region
○ When the electric and magnetic fields combine they form the electro-magnetic field
● Electric charge
○ It is a property of the particles that make up atoms
○ Charge is measured in coulombs
● Electron charge → -1.6 x 10^-19 C
● Proton charge → +1.6 x 10^-19 C
