9TH GRADE
PHYSICS
___
Notes
Formulas
● I = Q /t Q
I t
● V = IR V
I R
● E = Pt E
P t
● P = IV P
I V
● Total Current (IT)
○ Series - IT = I1 = I2 = I3
○ Parallel - IT = I1 + I2 + I3
● Total Voltage (VT)
○ Series - VT = V1 + V2 + V3
○ Parallel - VT = V1 = V2 + V3
● Total Resistance (RT)
○ Series - RT = R1 + R2 + R3
○ Parallel - R/n ← n = the number of identical resistors
■ Or 1/RT = 1/R1 + 1/R2 + 1/R3 ← if the resistors are not identical
Static Charge
● Static means stationary/not moving
● Static charge- electric charges that can be controlled and held in one place
, ○ Static electricity
○ Eg. rubbing a balloon on your hair
○ Combing your hair
○ Lightning
○ Electric shocking someone
○ Clothes clinging together
● Early scientists hypothesised there were two types of ‘electricities’
● Benjamin Franklin
○ Only one kind of ‘electrical fluid’
○ Build up of ‘electrical fluid’ - positive
○ Shortage of ‘electrical fluid’ - negative
● Idea of positive + negative still used to refer to electrical charge on object
● Last two centuries- theories have been developed about electricity based on particles
● Early scientists had no accurate way to detect static charge
○ Most common was to touch object and see if it delivers shock
○ 1748, french physicist + clergyman Jean Nollet invented electroscope
○ Electroscope- device that can be used to detect static charge
● Positive + negative charge in atom
○ All matter is made up of atoms- neutral
○ Nucleus = positive charge
■ Protons = positive charge
■ Neutrons = 0 charge
○ Electrons = negative charge
○ Solid material- nucleus vibrates but stays in same position at center of the atom
○ Electrons are outside the nucleus and move easily
■ Only electrons move in solid material
■ All solid materials charged by the transfer of electrons
■ If electron is removed, object/atom has overall positive charge
■ If electron is removed, object/atom has overall negative charge
○ Transfer of electrons charge solid materials + change charge on atoms
● Friction + electron transfer
○ Objects rub against each other- friction occurs
○ Can result in objects losing/gaining electrons
■ Eg. acetate- type of plastic used in film + overhead transparencies
■ When rubbed with paper towel, gains electrons, becomes negatively
charged
■ Paper towel loses electrons, becomes positively charged
● Insulators + conductors
○ Insulators- materials that don’t allow charges to move easily
PHYSICS
___
Notes
Formulas
● I = Q /t Q
I t
● V = IR V
I R
● E = Pt E
P t
● P = IV P
I V
● Total Current (IT)
○ Series - IT = I1 = I2 = I3
○ Parallel - IT = I1 + I2 + I3
● Total Voltage (VT)
○ Series - VT = V1 + V2 + V3
○ Parallel - VT = V1 = V2 + V3
● Total Resistance (RT)
○ Series - RT = R1 + R2 + R3
○ Parallel - R/n ← n = the number of identical resistors
■ Or 1/RT = 1/R1 + 1/R2 + 1/R3 ← if the resistors are not identical
Static Charge
● Static means stationary/not moving
● Static charge- electric charges that can be controlled and held in one place
, ○ Static electricity
○ Eg. rubbing a balloon on your hair
○ Combing your hair
○ Lightning
○ Electric shocking someone
○ Clothes clinging together
● Early scientists hypothesised there were two types of ‘electricities’
● Benjamin Franklin
○ Only one kind of ‘electrical fluid’
○ Build up of ‘electrical fluid’ - positive
○ Shortage of ‘electrical fluid’ - negative
● Idea of positive + negative still used to refer to electrical charge on object
● Last two centuries- theories have been developed about electricity based on particles
● Early scientists had no accurate way to detect static charge
○ Most common was to touch object and see if it delivers shock
○ 1748, french physicist + clergyman Jean Nollet invented electroscope
○ Electroscope- device that can be used to detect static charge
● Positive + negative charge in atom
○ All matter is made up of atoms- neutral
○ Nucleus = positive charge
■ Protons = positive charge
■ Neutrons = 0 charge
○ Electrons = negative charge
○ Solid material- nucleus vibrates but stays in same position at center of the atom
○ Electrons are outside the nucleus and move easily
■ Only electrons move in solid material
■ All solid materials charged by the transfer of electrons
■ If electron is removed, object/atom has overall positive charge
■ If electron is removed, object/atom has overall negative charge
○ Transfer of electrons charge solid materials + change charge on atoms
● Friction + electron transfer
○ Objects rub against each other- friction occurs
○ Can result in objects losing/gaining electrons
■ Eg. acetate- type of plastic used in film + overhead transparencies
■ When rubbed with paper towel, gains electrons, becomes negatively
charged
■ Paper towel loses electrons, becomes positively charged
● Insulators + conductors
○ Insulators- materials that don’t allow charges to move easily
