* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download P4C
Electric machine wikipedia , lookup
Ground loop (electricity) wikipedia , lookup
Mercury-arc valve wikipedia , lookup
Stepper motor wikipedia , lookup
Voltage optimisation wikipedia , lookup
Fuse (electrical) wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Portable appliance testing wikipedia , lookup
History of electric power transmission wikipedia , lookup
Three-phase electric power wikipedia , lookup
Electrical substation wikipedia , lookup
Buck converter wikipedia , lookup
History of electromagnetic theory wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Electrical ballast wikipedia , lookup
Opto-isolator wikipedia , lookup
Surge protector wikipedia , lookup
Skin effect wikipedia , lookup
Current source wikipedia , lookup
Overhead line wikipedia , lookup
Circuit breaker wikipedia , lookup
Single-wire earth return wikipedia , lookup
Rectiverter wikipedia , lookup
Ground (electricity) wikipedia , lookup
Stray voltage wikipedia , lookup
Mains electricity wikipedia , lookup
National Electrical Code wikipedia , lookup
Alternating current wikipedia , lookup
P4C Electrical circuits electrical current is the rate of flow of electrical charge A resistor is added to a circuit to limit the amount of current in it. Adding a larger resistor reduces the flow of current, so the current is smaller. A variable resistor/rheostat is made of a length wire. The length wire of a circuit can be changed. Longer wires allow less current to pass (Imagine going through a crowd to reach downstairs) thinner wires also allow less current to pass (imagine going through a thin corridor with loads of people, will you get through) Electric current In an electric circuit, charge is carried by negatively charged electrons the electrons are free to move.They flow in the opposite direction. If a circuit has a large resistance it is hard for the charge to move.In this case the rate of flow of charge (off current) is small. A variable resistor (or rheostat) can be used to change the resistance and current in a circuit. The slider alters the length of the wire in the circuit. The longer the length of the wire: the bigger it's resistance the smaller the current the dimmer the lamp Resistance = Like friction, Resistance is a force that is opposing another force The current in the circuit is measured in amps (A) using an ammeter, it is connected in a series circuit (one circuit) Voltage The force motivating electrons to "flow" in a circuit is called voltage. Voltage is a specific measure of potential energy that is always relative between two points Voltage is measured in volts, using a voltmeter.A voltmeter is always connected in a parallel circuit (more than one circuit) For a fixed resistor , as the voltage across it increases the current (flow of electrons) increases. For a fixed voltage, as the resistance increases the current decreases. Live, earth and neutral wire The live wire carries the voltage into and around the house The neutral completes the circuit, because electricity normally flows in through the live wire and leaves from the neutral wire The earth wire and fuse are for safety and work together. The earth wire creates a safe route for the current to flow through if the live wire touches the casing. You would get an electric shock if the live wire inside an appliance, such as a cooker, came loose and touched the metal casing. However, the earth terminal is connected to the metal casing so that the current goes through the earth wire instead of causing an electric shock. if the application (oven ect)develops a fault e,g, the live wire touches the case, there is suddenly as large current in the live wire and earth wire, if the current becomes too large the fuse melts, stopping the flow of charge A the fuse is in the live wire , the appliance is now disconnected from the mains supply, it is safe to touch. However the fuse must be replaced otherwise it would not work. The flex (cable) cannot overheat and cause a fire. Further damage of appliance is prevented. Mains electricity ( the thing you put the plug in) Double insulation: a double insulated appliance does not need an earth connection. It has a plastic case with no electrical connection (so if the live wire touched the case nothing would happen as it would not take the shock) or non conductor, it cannot become live. Circuit breakers The Re-settable fuses (circuit breaker) does the same job as the fuse, but it works in a different way. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem.