⚡Electricity/Electrical system ⚡

Electricity

Flow of electric charges

Circuits

Open circuit

Also called is an incomplete circuit

closed circuit

No electricity flows

Can be cause due to a break in the protective devices

Electricity flows continuously

materials that flow electricity

Conductors

Resistors

Insulators

Allow electricity to pass through easily.

Do not allow electricity to pass through them

Limit or regulate the amount of electricity

Type of circuits

Series

Parallel

Arranged one after one in a single loop or branch

Arranged in multiple loops or branches

Only one path for electricity

Advantages: simple built

Disadvantages: when more loads added the total resistance increase

When one load is damaged, affects the functionality

More that one path for electricity

Advantages: more loops the total resistance decreases

When one load is damaged does not affect the circuit

Currents(A)

SI unit for the electric current is the ampere(A)

The rate of flow electric charges

It has a symbol of /

A power source has two terminals-positive and negative cells

Energy supplied by the cells forces electrons to move out from the negative terminal of the source.

Energy flows back to the positive terminal of the source.

One energy of the source is used up eventually and not the electrons

The flow of electrons from the negative thermal to the positive terminal of a power source is called electron flow

Potential difference

Measuring electric current need a ammeter.

Must be connected in series

The electrical energy required to move a unit electric charges across the two points of an electrical component

Also called voltage

SI unit of potential difference or voltage is volt.

Have a symbol of V

Measuring potential difference

A voltmeter used for measuring potential difference across the two points of electrical components

Voltmeter must be connected in parallel across the electrical components

voltage circuit

Series

Parallel

V=V1+V2+V3

V=V1=V2=V3

Resistance

Circuit

Opposes the flow of electric charges through it

Equation:Resistance=voltage/current

SI unit is the ohm(Ω) has a symbol of R

Series circuit

Parallel circuit

Total resistance R=R1+R2+R3

1/R=1/R1+1/R2+1/R3

Short circuit

A short circuit is a closed circuit without any loads

Resistor

Fixed resistors

provide a specific resistance to regulate the amount of current flowing in a circuit

maintain a fixed amount of current

set up a desirable voltage

Reduce the amount of current flowing through a circuit

Act as energy converters

Has one fixed resistance cannot be changed

Mainly used to reduce the amount of current and voltages in electrical components

Variable resistance

Can be changed to give a range of resistance

Uses

Control the volume of a radio

control the speed of a fan

regulate the temperature of an electric iron

Effects of electric current

Heating effect

Different materials have different resistance

The greater the resistance a material has, the greater the amount of heat energy is produced

Electrical energy can be converted into heat energy

Magnetic effect

Electromagnet lose their magnetism when the electric current stop flowing

Electrical energy can produce a magnetic effect

Chemical effect

Electric current can produced a chemical change called electrolysis

Practical electricity

Power

Rate of converting electrical energy into other forms of life

Formula:Power(W)=Energy(J)/Time(S)

Cost of electrical energy consumption

An electric meter a device which is used to measure the amount of electrical energy

The unit of electrical energy measured by electric meters is the kilowatt-hour(kWh)

1 unit of electric energy=1 kWh

2 steps to calculate cost of energy

Amount of electrical energy consumed

calculate the cost of electrical energy consumed

Energy consumed(kWh)=power(kW) x Time(h)

electrical energy consumed=units of electrical energy consumed x cost per unit

Electricity safety

3-pin plugs

neutral

earth

Live wire

Marking:L

Marking:N

Marking:E

Colour:Brown

Colour:Blue

Colour:Green and Yellow

Normal function(current):Present

Normal function(current):Present

Normal function(current):Absent

Potential difference:Low

Potential difference: Low

Potential difference: High

Safety device

Fuse

Features:A capsule containing a short wire

When there is a too large current flowing in the circuit the wire melts and break the circuit

Earth wire

Circuit breakers

Contains main switch,miniature circuit breaker earth leakage circuit breaker

prevents excessive amount of electricity from flowing in the household circuit

Protective layer has green and yellow strip. Lower-resistance copper wire

Connects the metal casting of the electrical appliances to the ground

Function: carries the current to the appliance

Function: carries the circuit back to the original power source

Function: to protect the sudden damage of the electrical appliances or the electrical instruments due