⚡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