Physics

Electricity; Work, Power, Force

electricity

prescence and flow of electric charges

electric current

flow of charged particles or current

electricity

prescence and flow of electric charges

electric current

flow of charged particles or current

current in metal

due to movement of electrons

ammeter

used to measure currents

rate of flow of charge

ammeter measures what

electric potential

electric current is only present if there is ____ between two points

electric current in a wire

the net amt of charge that passes through the wire’s full cross section at any point per unit time

Q = charge; t = time interval

current formula

direct current

if the charges move around the circuit in the same direction at all times

• ex: batteries

Alternating current

if the charges move first one way and then the opposite way

• changes its direction each half-cycle

  • ex: household current

electric circuit

conducting path that allows a charge to flow from one terminal to another

purpose of battery

produce potential difference, which can make charges move

Resistance

measure of the opposition it offers to the flow of electric current

• SI unit is Ohm

resistor

wire or electrical device that offers resistance to electrical flow

resistance

what causes electrical energy to be converted into heat

Resistance

depends on the conductor’s

• length

• cross-sectional area

• type of material

• temp

resistivity

property of the conductor to which it offers resistance to the flow of current through it

resistance

the better the conductor the less its?

Ohm-meter

SI unit for resistivity

resistor

electrical component that limits or regulates the flow of an electrical current in an electronic unit

brown

1% tolerance

red

2% tolerance

Gold

5 % tolerance

Silver

10 % tolerance

no color

20% tolerance

black

number 0; multiplier 1

brown

1

red

2

orange

3

yellow

4

green

5

blue

6

violet

7

gray

8

white

9

gold

-1

silver

-2

Ohm’s law

the higher the electric potential difference or voltage, the more charges can move

George Ohm

discovered Ohm’s law

voltage

aka electromotive force

voltage

quantitative expression of the potential difference in charge between two points in an electrical field

resistance

hindrance to the flow of charge

Current

Unit of measurement: Ampere

Volatage

Unit of measurement: Volt

Resistance

Unit of measurement: Ohm

electric power

rate at which electric energy is converted into another form such as mechanical energy, heat, or light

Electric Power

equal to the product of the current and voltage

power

energy per unit time (watt)

energy

power x time (ex: kWh)

electric circuits

any path along which current and electrons can flow

electromotive force (EMF)

maximum potential difference across the terminals is provided and maintained

direct current circuit

• mostly used in low voltage applications.

• resistor is main component

series circuits

Two or more loads are linked across a single loop of wire

• The current is the same at all points

• Total resistance to current in this circuit is the sum of the individual resistances along the path.

parallel circuits

different loads are situated on different wire loops.

• Junctions

parallel circuits

• Components connected all have the same voltage.

• Each path operates independently of the other paths.

• Total current in this circuit equals the sum of the currents

• As the number of branches is increased, resistance of the circuit is decreased

parallel circuits

these types of circuits are prone to overloading

Mild tingling sensation

0.001 A

Muscle spasms (“can’t let go”)

0.01-0.02 A

Fatal (heart fibrillation)

0.2A

120 volts

household current voltage that can stop one’s heart

extension cords

may not be used as permanent wiring and should be removed after temporary use for an activity or event.

surge suppressors with built in circuit breakers

may be used long-term and are available with three, six and 15 foot-long cords.

work

done when there is motion (scalar quantity)

Joule

work is measured in

work against inertia

applying force to cause change in motion

• ex: throwing/ kicking a ball

• W = Fd = mgh

work against gravity

• involves height

• W = mgh

Gravitational Potential Energy

stored as the result of the gravitational attraction of the earth for the object

• mgh

• directly proportional to both mass and height

kinetic energy

energy of an object in motion

• once object at rest starts moving

Work-Energy Theorem

states that the net change in KE of a particle is equivalent to the sum of work done by all types of external forces

• KE increases as a result of the amt of work. work done on an object transfers energy to the object

mechanical energy

energy that is possessed by an object due to its motion or due to its position

mechanical energy

sum of KE and PE of an object

potential energy

as an object is falling what decreases?

kinetic energy

as an object is falling what increases?

conservation of energy

PE lost during motion is converted to KE

constant

mechanical energy stays?

law of conservation of energy

energy can neither be created nor destroyed, but can only be converted from one form to another

4186 joules

1 Kcal =?

food

type of chemically stored energy

• in kilocalories

power

rate at which work is done and energy is expended

1KW

1000 Watts

1MW

1 × 10^6 Watts

1 HP

746 watts

1 HP

0.746 KW

1 HP

550 ft-lb of w/s