physics 1) Electricity and Magnetism

a. electric charge static electricity and coulombs law b. electric fields c. electric current, voltage, resistance, and ohm's law d. Series and Parallel circuits e. electrical power

What is electric charge?

property of matter that causes it to experience a force when placed in an electromagnetic field

Unit for electric charge

Coulombs, C

Electric charge of protons equation

1.60 × 10^-19 C

Electric charge of electrons equation

-1.60 × 10^-19 C

Like charges ……., unlike charges …….

repel, attract

What is an electrical conductor? and 3 examples

substances which allows the transfer of electrons

• water

• copper

• graphite

• gold

• metals

what is an insulator? 3 examples

substance which does not allow the transfer of electrons

• Plastic

• rubber

• glass

• fabric

what is electricity?

• form of energy which occurs because of charge particles

• can build up in one place or can flow from one place to another

what are the 2 main forms of electricity?

static and current

static electricity

• when electrons gather in one place (Stationary on surface of object)

• due to electric charge that builds up on surface of insulator

• charge that built up cannot easily flow away from the insulator

• can build up when 2 materials rubbed together

  • electrons are transferred from one material to the other. one material ends up with fewer electrons meaning that one has positive and one has negative charge. (opposites attract)

current electricity

• involves electrical energy which travels in a circuit

what is the name of the force between two materials that are rubbed together?

friction

what happens when an insulator made of polythene is rubbed with a cloth'?

electrons move from cloth to insulator

what happens if an insulator made of acetate is rubbed with cloth

electrons move from insulator to cloth

process of rubbing ballon to wall (static electricity)

1. rub baloon on woolen jumper

   1. transfers electron onto balloon by friction

   2. balloon becomes negatively charged while jumper is left positively charged

2. balloon placed near wall (neutral wall)

   1. positive charges in wall brought to surface because they are attracted to the neg charge of balloon

3. balloon sticks to wall

   1. because opposite charges attract

4. Sticks to wall because of electrostatic attraction

how is sparking or electric shock caused?

• caused by build up of electrostatic charge

• occurs when

  • two objects charged by friction become oppositely charged

  • surplus of eletrons causes electrons to jump actoss to an object that is neutral

static electricity on carpet (shock when you shake hands)

1. carpets have tendency to have static electricity build up

2. electrons travel from carpet to person whose shoes are rubbing the carpet

3. when that person shakes hands with uncharged person, electrons jump to them

4. This causes a shock

static electricity- lightning

1. when clouds move over eachother, they become charged when electrons transfer between them

2. ground is neutral so neg charges from cloud jump to positive charges on ground creating huge spark called lightning

4 uses of static electricity

1. photocopiers

2. printers

3. spray painting

4. pollutant removers

who found coulomb’s law?

charles augustin de coulomb

what is coulombs law?

measuring the electrostatic force between 2 charges.

proportional & inversely proportional

• magnitude of force F between the chargesis proportional to their product (q1xq2)

• inversely proportional (one increases, one decreases) to the square of distance between them

Equation for coulombs law

F=. kQ1Q2 / r²

force= coulombs constant x charge 1 x charge 2 / squared distance

what is coulomb’s constant (k)

9×10^9 Nm/C²

Electric Current (I)

rate of flow of electric charge in a circuit from pos to neg terminal

charge is measured in …

Coulombs C

current is measured in …

amperes A

Ohms Law pyramid

Types of current

1. direct current (dc)

2. Alternating current (ac)

Direct Current DC

current that is steady, constantly flowing in the same direction in a circuit from pos to neg

• VOLTAGE AND CURRENT MAINTAINS IN ONE DIRECTION

everything that runs on a battery and uses a AC adapter while plugging into wall or uses usb cable for power relies on DC

ex: phone batteries, flashlight, television

Alternating current AC

continuously changes its direction going back and forth around a circuit

• VOLTAGE AND CURRENT CHANGES DIRECTION ALTERNATIVELY

ac is most commonly used for houshold equipment as it makes transporting AC across long distances is relatively easy

Voltage V

the push or force that makes electric charges move through a wire or a circuit

• in electricity voltage makes electrons move and creates flow of electric current

• Voltage is also known as potential difference

• measured in volts

Electrical resistance R

• obstruction/opposition to current

• measured in ohms (Omega sign)

who discovered ohms law

german physisist georg ohm

main statement of ohms law

“current is directly proportional to voltage as long as temp remains constant?

Diode

component in circuit that allows current to only flow in one direction

What is an electric circuit

• a path for electric charge to flow along

• needed for circuit to work: source of energy, component, complete loop

Cell in circuit

provides circuit with source of potential difference (Energy)

Battery in circuit

2 or more cells

Switch in circuit

used to turn circuit on (closed) or off (open)

resistor in circuit

limits flow of current

Motor in circuit

converts electrical energy to mechanical energy

diode in circuit

allows current to flow in one direction only

used to convert AC to DC

light emmiting diode (LED) in circuit

emits light when current passes thru it

ammeter in circuit

used to measure the current in a circuit. it is connected in series with other components

Voltmeter in circuit

used to measure the voltage of an electrical component

it is connected in parallel with relevant component

bulb or lamp in circuit

uses electric current to emit light

Fuse in circuit

protects expensive components from current surges and act as a safety measure against fire

Main rules of drawing circuits

1. rectangular shape

2. straight lines

3. correct symbols for each components

4. all lines touch accurately

5. components in cneter of wire

types of circuits

series and parallel

series circuit

• a single loop or pathway in which the componenets are connected one after another

• Current is same,

• Voltage is shared,

• resistance adds up

parallel circuit

• a parallel circuit is one which contains a point (junction) where current can split (point a) or join (point b)

  • more than one path

• CURRENT: Splits at first junction, joins together at second junction

  • Splits at each strand

    • A1=(A2+A3)=A4

    • If bulbs are identical then current will split evenly, but if they are not the current will not split evenly

• VOLTAGE: voltage across cell/battery is the same as the voltage across each branch

  • Voltage stays the same

    • V1=V2=V3

• RESISTANCE: when resistors are connected in parallel, combined resistance decreases and is less than the resistance of any of the individual components

  • 1. = 1. + 1

    ---

    Rtotal. R1. R2

  • SUMMARY PARALLEL: current is shared, total voltage is same, total resistance decreases

What is an electric field

a region where a charged particle will experience a force

• can be represented by electric field lines

electric field line always point away from ……. charges and towards ………charges

positive, negative

what happens when the charge entering electic field is same ( neg, neg or pos, pos)

they will be repeled and move away from the charge creating the field

what happens if the charges entering entering an electic field oppose

they will be attracted and will move towoeds the charge creating the field

the force becomes ….. as the distance between the 2 charged objects …… and vice versa

stronger, decreases

the strenght of an electric field is determined by ……

• a stronger field is represented by lines ….

• a weaker field is represented by line …….

spacing, closer. further

Rules of electric field drawing

• field lines never intersect

• lines are perpendicular to surface of charge

• start point of the field lines is at the positive charge and end at neg charge

Electric Field strenght (E)

the force experienced per unit charge of the particle in the field

Equation for electrical field strength

electrical field strenght= force/charge

E=F/Q

electrical power

the rate of energy transfer or the amount of energy tranfered per second

• power of a device depends on: voltage & current

equations for electrical power:

Power=current voltage

P=IxV

P=I²xR

P=V²/R

---

if current or voltage doubles the power will be 4 times as great

I is current, V is voltage, and P is power, R is resistance

power is measured in …

watts (W)

Current is measured in …

Amps (A)