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Electrical System (Final) - Coggle Diagram
Electrical System (Final)
Flow of electricity
electric current
measured by the amount of electric charge flowing through
any
point in a closed circuit per unit time
Rate of flow of electric charges
form of energy
Secondary energy source, converted from primary energy sources like fossil fuels
SI Unit: Ampere (A)
Electric circuit
Connecting conductors and electrical source to form closed circuit for electric current to flow through
Components
Switch
Close/open circuit (not necessary)
Conducting wire
Provide a path of low resistance for electrical current to flow
Electrical load
Consumes electric power eg. light bulb
Electrical source
Drive electrical current around closed circuit eg. dry cell
Symbols
represent electrical components
easier to study circuit
Closed/ Open circuit
If path has a break point, it is open, electric charges stop moving
Electric charges flow continuousy in closed circuit
Parallel/Series Circuit
Series
When more loads added, total resistance in circuit increase
A damaged load affects functionality of other loads
Electric current same in every point in single loop, identical or different
Parallel
Total resistances decreases with more loops
Damaged load does not affect other loads
common connection of circuits in households
Each loop has specific amt of electric current, total current must add each loop
Types of current
Convention current: positive charges more from positive to negative terminal (left to right)
In reality, movement of electrons is responsible for electric current, in electron flow, flow from negative to positive terminal
Electrical components
Ammeter
SI Unit: Ampere (A)
measure electric current flowing through a circuit
must be connected in series with other electrical components
negative and positive terminal of ammeter must correspond with dry cell
since current flowing through light bulb is supplied by dry cells, it measures current flowing through circuit and not just through light bulbs
if connected in parallel, check if the electric charge passes through the ammeter
Voltmeter
energy is required to move electric charges from one point to another of electrical components
potential difference is the electrical energy required to move a unit electric charge across the two points of an electrical component, also known as voltage
difference in energy between two points
SI Unit: Volt (V)
eg. electrical component of 3V means that 3J of ee is needed to move a unit of electrical charge across two points of the component
used to measure pd across two points
a positive charge will always flow from a point of higher to lower potential
Arranged in parallel to/across electrical load (light bulb)
If arranged across all electrical loads, it also measures pd of dry cell, since it is equal in pd
Has to connected parallel to electrical component, does not measure all electrical components unless as stated above
Resistor
Resistance
The characteristic of a material that opposes the flow of electrons or electrical charges, ratio of pd across component to
current
passing through component
V= pd I= current R= resistance
SI Unit: ohm (Ω)
every electrical component resists the flow of electric charges when connected in a circuit
The higher the resistance, the higher the potential difference needed to move the electric charge through the
electrical component, the smaller the electric current flowing through
Series circuit: More resistors inside = more resistance, total resistance determined by reciprocal relat.
Parallel: net resistance decreases as there are more paths for current to pass through, total current is the sum of each branch, total resistance is sum of all ee component resist.
effective resistance decreases
Resistors
Fixed resistor
resistance of resistors cannot be varied
used to reduce amount of current and voltage in electrical components
Variable resistor
resistance of resistor can be varied, can be adjusted lower or higher
Control/regulate smth
Dependent on factors
Length
increase length- increase resistance, electric charges have shorter distance to flow
Cross-sectional area of electrical component - thickness of wire
increased cross sectional area decreases resistance (thicker), more electric charges can flow through
Type of material
electrical wires made of copper since it has lower resistance and good conductor of electricity
Effect of electric current
Heating effect
Causes conversion of electricity to thermal energy, producing heat, usually in electric appliances
Magnetic effect
strength of electromagnet increased by:
increase no. of turns around wire
increase amt of current
winding coil around iron core
iron
rod found near or placed inside a solenoid (coil of wire), electric current flows in wires, inducing them to be magnetised to an electromagnet, which as north and south magnetic poles creating magnetic field
commonly used in door bells, telephones and magnetic cranes
Chemical effect
Electrolysis
chemical method to
break down (decompose) a compound into its respective elements (chemical change)
Electroplating
coating an object with a layer of metals
eg. aluminium can be extracted from bauxite by passing electricity through molten bauxite in a process called electrolysis
prevent object like iron/steel from rusting/enhance shininess
Extracting pure metal from impurities
extract pure samples from its impurities
Household Electricity in SG
25.82 cents per unit, with unit referring to kilowatt hour
unit cost is pegged to fuel price and price of natural gas, hence it fluctuates according to the global price of fuel and price of natural gas from Malaysia and Indonesia
use of electricity in Singapore increases as technology advances
Power (of an electrical component) - amount of (electrical) energy that is converted to other forms of energy (per unit time by electrical component)
W = Power, J = Energy S = Time
1 W means 1J of electrical energy converted to thermal energy in 1 second
1.0 kW = 1000 W
kWh = kW x h
Electrical appliance
time factor and wattage affects amount of electrical energy used, but more appropriate to discuss energy usage in terms of power
SI Unit: (W) watt
higher power rating means more electrical energy converted in a second
electricity meter measures the amt. of electrical energy consumed
Electric plugs, fuses, wires etc.
3-pin plug
used to connect an electrical appliance to power circuit sockets
three types of wiring
Live wire: Brown, current present (ard 240V in sg), high potential difference (less resistance)
Neutral wire: Blue, current present, low potential difference, 0V
Earth wire: Green and yellow, no current, low potential difference, connected to metal casing of electrical appliance, connected to the ground (0V), low electrical resistance, only carries electricity when live wire faulty
Fuse: short thin piece of wire that melts when
current exceeding its rating
flow through, prevent electrical hazard, another fuse with same rating needs to replace it to work again, needs to be connected to live wire, higher rating than appliance
Scenario: If live wire touches the metal casing and appliance is switched on, the current flows from the live wire to the ground. Low resistance results in high current. Fuse will melt to disconnect the circuit or the Earth Leakage Circuit Breaker will trip to disconnect household electricity supply
Scenario, electrical fault: Live wire touches the metal casing, electricity will not be conducted to the earth
If earth wire not present, when live wire touches metal casing, it becomes 'live', current flow through user to earth when touch live metal casing, electrocution
Circuit breaker
prevent excessive amt. of electrocity flowing in households
'trips' to open circuit
Hazards of Electricity
Electric shocks
electric current passes through body
Voltage greater than 50V
Current passing through body greater than 1mA
high voltage and current is classified as electrocution
Electrical fault
Live wire touches metal casing which becomes live. Large potential difference between metal casing and ground.
If person touches metal casing, current flows through body into ground
Electric fire
large current flows through electric wires, generating heat and melting insulation, starting fire
factors
Overloading
too many appliances connected to same power socket, draws large current, generating heat and melting insulation, causing a fire
frayed/damaged wires
person who touch bare wire, will have current flowing through them
wet conditions
water is conductor of electricity
short circuit
refers to a closed circuit without any loads (consume electricity), reduces effective resistance of a circuit, resulting in generation of large current, causing a fire
Prevent electrocution
never overload electrical outlet, as it generates much current and heat, melting insulation
never insert objects into electrical outlet
repair or replace when insulation of electrical wiring is peeled off, as it exposes wires
Switch off appliances and pull plug out when in contact with water, never use near water source
Use electrical appliance with dry hands
