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chapter 13 electrical system - Coggle Diagram
chapter 13 electrical system
flow of electricity
current: electrical current is the rate of flow of electric charge. (si unit: amphere (A))
an ammeter is used to measure the amount of current in the circuit
parallel: has two or more path for the current to flow. current flowing through each branch maybe the same or different, but is always less than the curerent flowing out from the source. a break in any branch does not stop the flow of the current in the remaining branches
series: has only one path for the current to flow. the current that flows through each component is the same. a break in any part of a series curcuit cuts the flow of the current in the whole circuit
potential difference: the p.d. between any two point is the amont of energ needed to move one unit of electrc charge from one point to another SI unit: volt (V)
an voltmeter is used to measure the amount of voltage or potential different in the circuit
the higher the voltage across an electrical component th bigger the current flowing through it
resistance: resistance of a component is the ration of the potential difference across it to the current flowing through it. SI unt: ohm (Ω)
formula: resistance = p.d. (V) / current (I)
fixed resistor: resistance value is fixed
variable resistor: resistance value is variable
when resistor is connected to series circuit: totale resistance of circuit increase the curerent in the circuit decrease. when 2 or more resistor are connected, the total resistance is always the sum f the resistance of each of the resistor. (2Ω + 3Ω)
when resistor is connected in parallel circuit: the total resistance decrease and current increase. the total resistance is always lesser than the resistance of either of the resistors (1/2+1/4)-1
convection and electron flow
electron flow: movement of negative charge form the negative terminal to the positive terminal
convection current: flow of positive charge from the positive terminal to the negative terminal
effects of an electric current
extraction of metal
process called electrolysis. break down compounds into elements
electroplating
coating objects with metal by immersing them in a liquid passing an electrical current through liquid
magnetic effects
electric currents in the wires produces magnetic effects around wire which cause the wore to be magnetic. effect can be increased by making current flow in a coil of wire called solenoid.(electromagnet: created from iron rod placed inside a solenoid)
heating effect
when electrical current passes through a wire, electrical energy is converted into heat. The heating element (nichrome) is covered with a layer of electrical insulation. insulated element is in turn placed in looped tune made of good conductor
lighting effect
heating effect of electric current can lead to lighting effect
household electricity
hazard of electricity
electrical fires: large curr3ent can occur when electrical circuits are damaged or misused (inserting too much plug in the socket overloading) large current generate heat which melts the insulator and cause fires
electrocution: large current are dangerous when they pass through a person's body.
prevention
do no use electrical appliances in damp places
do not touch electrical appliances with wet hands
switch off electrical appliances and pull out plugs when not using
avoid getting water into the socket of appliances
so not use an appliance until you are sure it's dry
do not touch exposed wire and call an electrician to repair damage appliances
never insert anything into electrical socket
power
amount of electrical energy converted to other form of energy per unit time by component
SI unit: watt
formula: power = energy/time
amount of electrical energy used formula: energy = power x time
conversion of 1kW and used for 1hr: 1kWh = 1kW x 1hr
safety feature
fuse
make use of the heating effect of an electric current to switch off large current
large current causes a short, thin wire to heat up and melt
connection to live wire is rated with current that melt the wire in it. when the wire in a fuse melt, the fuse in 'blown'
circuit breaker
a circuit breaker can cut off electrical current. it does not need to be replaced
earth wires
neutral wire (blue) (0v)
live wire (brown) (240V)
earth wire (yellow-green) (0V) (provid3es a path of low electrical resistance. large current flows directly from the live wire into the ground) (current always choose to flow through least resistance)