BASIC OF ELECTRICAL

ELECTRICITY

PEOPLE

Benjamin Franklin

Thomas Edison

Have you heard of these people? Why are they important?

Benjamin FranklinProved that lightning was electricity by

flying a kite in a lightning stormHelped people understand the principles

of electricity

• Thomas Edison– Invented the electrical light bulb

Definition:

Electricity is a form of energy that can be easily changed to other forms.

What is Electricity???What is Electricity???

WHERE DOES ELECTRICITY COME FROM?Mainly 2 sources:1) Power Stations

- Supply a lot of electricity- Used in many electrical appliances

2) Electric Cells (batteries)- Supply a little electricity- Portable- Safe

HOW DOES AN ELECTRICAL APPLIANCE WORK? To make an electrical appliance work, electricity

must flow through it.

The flow of electricity is called an electric current.

The path along which the electric current moves is called the electric circuit.

What is an Electric Current???

What is an Electric Current???

Definition:

An electric current is the rate of flow of electric charges in a circuit.

connecting wire

electric cell

filament

flow of electrons

ELECTRIC CHARGES

Electric charges are made up of positive charges (protons) and negative charges (electrons).

When these charges flow in a circuit, a current is produced.

HOW DOES ELECTRICITY FLOW?

The battery in a circuit gives energy to the electrons and pushes them around a circuit, from the negative terminal of the cell, round the circuit and back to the positive terminal of the cell.

HOW TO MEASURE CURRENT?

The SI unit for electric current is ampere (A).

Smaller currents are measured in milliamperes (mA).

Different electrical components and appliances require different sizes of current to turn them on.

1 A = 1,000 mA

1 mA = 0.001 A

1 A = 1,000 mA

1 mA = 0.001 A

INSTRUMENT TO MEASURE CURRENT An ammeter is an instrument used for

measuring electric current.

AMMETER It must be connected in series in the circuit.

Positive side of ammeter must be connected nearest to the positive terminal of the battery (electric cell), and vice versa.

VOLTAGE An electric cell gives energy to the electrons

and pushes them round a circuit. Voltage is a measure of how much energy the electrons receive.

Different voltages are supplied by different cells and batteries.

12 V Car Battery

1.5 V Dry Cell

9 V Dry Cell

HOW TO MEASURE VOLTAGE?The SI unit for voltage is volt (V).

A voltmeter is an instrument used for measuring voltages.

VOLTMETERVoltmeters must be connected in parallel to the circuit.

The positive side of voltmeter is connected to the positive terminal of the cell, and vice versa.

DIFFERENCE BETWEEN VOLTS AND AMPS Example – you could

say that… Amps measure how

much water comes out of a hose.

Volts measure how hard the water comes out of a hose.

measuring currentSERIES CIRCUIT

PARALLEL CIRCUIT

• current is the same at all points in the circuit.

2A 2A

2A

• current is shared between the components

2A2A

1A

1A

measuring voltage

PARALLEL CIRCUIT

SERIES CIRCUIT

• voltage is the same at all points in the circuit.

• voltage is shared between the components

RESISTANCEWhen an electric current flows through a

circuit, there will be some resistance that opposes it. (similar to friction)

It can be measured by dividing voltage by the current.

R = V

I

R = ResistanceV = VoltageI = Current

RESISTANCEGood conductors of electricity have LOW RESISTANCE. (Eg. Metal objects)Electricity is able to flow through

them very easily

Poor conductors of electricity have HIGH RESISTANCE. (Eg. Wood, cloth)Electricity is not able to flow

through them easily

The SI unit for resistance is ohm () Different electrical components have different

resistance For example, nichrome wires have a higher

resistance than copper wires.

Resistance

So should we use nichrome or copper to make wires?

EXAMPLE 1An electric rice cooker operates at 240 V and uses a current of 8 A. What is the resistance of the rice cooker?Voltage (V) = 240 VCurrent (I) = 8 A

R = V

I

R = 240

8

= 30

RESISTORS An electrical component that is specially made to

have a certain resistance is called a resistor. They can be connected in a circuit to resist the

current flow.

FIXED RESISTORS AND VARIABLE RESISTORS Fixed resistors have only one resistance

value Variable resistors can be adjusted to

change the resistance.

fixed resistor symbol variable resistor symbol

•Variable resistors are useful in light dimmers and other electric appliances

S/E: RESISTORS Resistors can be connected in series or parallel

single resistor

extra resistor in series results in

dimmer bulb

extra resistor in parallel results in brighter bulb

Resistors connected in SERIES

Resistors connected in PARALLEL

S/E: RESISTORS IN SERIES When resistors are

connected in series, the resistance will add up and increase.

R = R1 + R2 + R3…2 3

The total resistance for this circuit is:

2 + 3 = 5

S/E: RESISTORS IN PARALLEL When resistors are

connected in parallel, the resistance will decrease

This is because they will provide alternate routes for the current to flow.

S/E: RESISTORS IN PARALLEL

6

6

1

R=

1

R

1

R

1

R+ +

1 2 3

What is the resistance of the circuit?1

R=

1

6

1

6+

1

R=

2

6

1

3= R = 3 The final

resistance is smaller

WHAT WE KNOW...

Definition Units Symbol

Current The rate at which electrons move from one place to another

Ampere (A)

I

Voltage (Potential Difference)

Measures the amount of energy given to electrons to move them

Volt (V) V

Resistance

Degree to which a substance opposes the flow of electric current through it

Ohms (Ω) R

DC CURRENT

Direct current is the one way flow of electrical charge from a positive to a negative charge.

Batteries produce direct current. Direct Current is different than

alternating current because the charge only flows in one direction.

Thomas Edison is credited for promoting direct current.

ALTERNATING CURRENT Alternating Current is when charges flow

back and forth from a source. It is the way we receive our electricity (for

our houses, businesses, etc.) Nikola Tesla was a pioneer in the

advancement of alternating current. AC flows in the form of a sine wave, back and

forth. It is easier to transform voltages in AC. The purpose of transformers is to convert AC

voltages. Transformers are extremely important to AC

current, and our life.

Alternating Current Direct Current

Amount of energy that can be carried

Safe to transfer over longer city distances and can provide more power.

Voltage of DC cannot travel very far until it begins to lose energy.

Frequency

The frequency of alternating current is 50Hz or 60Hz depending upon the country.

The frequency of direct current is zero.

Direction It reverses its direction while flowing in a circuit.

It flows in one direction in the circuit.

CurrentIt is the current of magnitude varying with time

It is the current of constant magnitude.

Types Sinusoidal, Trapezoidal, Triangular, Square. Pure and pulsating.

Obtained from A.C Generator and mains. Cell or Battery.

NONRENEWABLE

ANDRENEWABLERESOURCES

HMMMM....What do you think

nonrenewable resources are?

Break it down...

Nonrenewable?

Resource?

NONRENEWABLE RESOURCES

A nonrenewable resource is a natural resource that cannot be re-made or re-grown at a scale comparable to its consumption.

NUCLEAR ENERGYNuclear fission uses uranium to create

energy.

Nuclear energy is a nonrenewable

resource because once the uranium is

used, it is gone!

COAL, PETROLEUM, AND GAS

Coal, petroleum, and natural gas are

considered nonrenewable

because they can not be replenished in

a short period of time. These are

called fossil fuels.

HOW IS COAL MADE ???

HOW ARE OIL AND GAS MADE ???

WHAT WAS THE DIFFERENCE BETWEEN COAL AND OIL/GAS?

HMMMM....

If nonrenewable resources are resources that

cannot be re-made at a scale comparable to its consumption, what are renewable

resources?

RENEWABLE RESOURCESRenewable resources are natural resources that can be replenished in a short period of time.

● Solar ● Geothermal● Wind ● Biomass● Water

SOLAR

Energy from the sun.

Why is energy from the sun renewable?

GEOTHERMAL

Energy from Earth’s heat.

Why is energy from the heat of the Earth renewable?

WINDEnergy from

the wind.

Why is energy from

the wind renewable?

BIOMASSEnergy from

burning organic or living matter.

Why is energy from biomass renewable?

WATER OR HYDROELECTRIC

Energy from the flow of water.

Why is energy of flowing water

renewable?

SUMMARYWhat are the differences between

nonrenewable and renewable

resources?

THERMAL POWER STATION

A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator.

SOLAR POWER PLANTSolar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam.

ELECTRIC MOTORAn electric motor is an electrical machine that converts electrical energy into mechanical energy.

ELECTRIC GENERATORIn electricity generation, a generator is a device that converts mechanical energy to electrical energy for use in an external circuit.