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Physics grade 9 notes (electricity)
Basic easy to read and follow physics notes that have gotten me through science class.
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10.1-Static ElectricityStatic electricity refers to electric charges that stay and build up in one place
When 2 substances are rubbed together, the force resisting their motion is called friction. this generates heat. friction causes
electrons to move from one substance to the other. Which substance loses it electrons depends on relative Electron affinity.
Electron affinity determines how well a substance holds onto its electrons .
If an object has more positive electrons its positive and if it has more negative electrons its negative
Substances Electron affinity Gain/Lose Charge
amber higher gain electrons negative https://qph.cf2.quoracdn.net/
cat fur lower lose electrons positive main-qimg-5647224ef811277
08744caf55d303a2d-lq
glass lower lose electrons positive
cotton higher gain electrons negative
plastic higher gain electrons negative
human hair lower lose electrons positive
wood higher gain electrons negative
nylon lower lose electrons positive
objects that have the same charge ( EX: +/+) they will repel each other. objects with different charges (+/-) will
attract each other.
How can charged objects attract neutral objects?
if you charge rub a balloon on your hair, the balloon will become negative. Holding the balloon near a neutral object (like a wall)
will make the electrons in that object move. The negative charges in the balloon will repel the negative charges in the object,
leaving only the positive charges close to the balloon, because opposites attract, the balloon will stick to the wall.
Chapter 10-Word Definitions
Word Definition Word Definition
materials that hold their electrons loosely, and a solid, liquid, or gas that resists or blocks the
insulator
Conductor allow electrons to move freely from atom to movement of electrons
atom. all metals are conductors
The movement or transmission of electrons
Conductions
Insulators materials that hold their electrons tightly and through a substance
do not allow electrons to move freely-charge
Electroscope An instrument that can detect static charge
Chapter 10 2
, Word Definition Word Definition
stays on the spot. all non metals are insulators Electrostatics the study of static electric charges
changed particles that exert on electric force The process of directing excess electricity to
Electric charges Grounding
on each other the ground (can be with a wire)
static charge/static electric charge that builds up on the surface of Electrical When electric charges are transferred very
electricity an object Discharge quickly
The tendency of a substance to hold on to the A grounded metal rod placed high on a
Electron Affinity
electrons LIghting rod structure to conduct electrical current from a
ability of materials to allow electrons to move lightning strike directly to the ground
conductivity
freely in them
10.2- Transfer Of Static Electric Charges
Charging By Conduction, Electroscope
you can figure out is an object is charged with an electroscope. An electroscope can detect static charge. an electroscope is
a metal sphere attached to a metal rod with thin metal pieces called leaves.
when the sphere( which is also called the knob) is charged, it spreads out over the entire structure. The leaves will spread
out , and the greater the charge, the more the leaves will separate.
you can also use a pith-ball electroscope to detect electric charges.
Methods Of Charging An Object
1. Charging by friction
2. Charging by conduction (contact)
3. Charging by induction (no contact)
Charging by Conduction takes place when physical contact is made between a charged object and a neutral object.
On contact, electrons flow from the negatively charged object into the neutral object. After the objects have touched,
the negatively charged object has a reduced charge but still a negative charge. However the neutral object is now
negatively charged. An object that becomes charged by contact (neutral object) always gets the same charge that is on
the object that charges it (same goes for if its positive)
Charging by Induction takes place when a charged object is close to a neutral object, the electric field of the charged
object produces a force on the neutral object. The charged object exerts a force on the protons and electrons in a solid
neutral object, but only electrons can move in the solid. Therefore the charged object causes electrons in the neutral
object to move. An induced charge separation is the movement
Chapter 10 3
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