1) Charging occurs through two methods: friction and induction. Friction charging involves rubbing two objects together, leaving one positively and one negatively charged. Induction charging involves placing a charged object near a neutral object, causing their charges to separate.
2) Electric fields originate from charged objects and can cause nearby charged objects to experience force. Fields are represented by electrical lines of force extending from positive to negative charges.
3) Current in electrical circuits is the flow of electrons. A complete circuit with a battery or cell is needed. Devices like ammeters and voltmeters can measure current and voltage in circuits.
12. Representing Fields
● An electric field is the area around a charged
object in which another charged object
experiences a force.
13. Representing Fields
● A charged object has a field
● If a charged object moves into the field, it
experiences a force.
● It can be shown by electrical lines of force
14. Representing Fields
● The field originates from the positive charge
● The field goes into the negative charge. This is
just like magnets( except ‘+’ is ‘N’ and ‘-’ is ‘S’)
15. Charged Particles
● Charge is measured in Coulombs (c), named
after Charles-Augustin de Coulomb.
● Electron is a negatively charged particle.
● It is much smaller that an atom (only weakly
attached to the atom itself)
● Proton is a positively charged particle
● Present in the nucleus
18. Current in circuits
● Current is the flow of electrons
● For an electric current we need -
– A completed circuit
– A cell or Battery
19. Current in circuits
● Current that flows in one direction all the time is
called d.c Current (Direct Current)
● Current that keeps changing direction is called
a.c current (Alternating Current)
● Current(I) = Charge(Q) / Time(t)
20. Conductors
● Good conductors include most metals including
copper, silver, gold, steel, etc.
● Good conductors are needed in a circuit for it to
run without much resistance.
● Bad conductors have more resistance, thus not
a good material for a circuit.
21. Insulators
● Good Insulators include most polymers (such
as Perspex or Polythene), minerals, glass, etc
● Good insulators are used to protect something
or someone from charges.
28. Lightning
● The strong negative charge in the cloud attracts
positive charges in the ground (by induction).
● The positive charges move to the tallest objects
● A stepped ladder of negative charge comes
down from the clouds, seeking a path to the
ground.
29. Van De Graff Generator
● A belt is spun, creating a charge.
● These charges move towards the sphere and
get evenly distributed.
● When the person touches the sphere, the
charges get transferred to the person.
31. Lighters
● Called a Piezoelectric generator(literally means
pressing electricity).
● A piezoelectric crystal is neutral, but not
symmetrically arranged
● When it is stretched, or bent, the charges
move, and thus giving the crystal a charge.
33. Capacitors
● A capacitor is made of 2 metal plates with a
dielectric metal between them.
● When a voltage is given, the plates will start to
accumulate an opposite charge.
● Whenever needed, the input will be inverted,
acting as an output.