Presentation on theme: "Electric Circuits. Danger – Do not attempt electrical work until you have learned the safe and proper technique from a certified electrician. Copyright."— Presentation transcript:
Electricity difference electrons negatively Electricity is a force created by a difference in charges (+ & -) due to gained or lost electrons. (an electron is a negatively charged particle.) electrons moving electrical current. When electricity is flowing between two points, this is actually electrons moving from point A to point B. This is called an electrical current.
difference in charges In order for these electrons to flow, however, there must be a difference in charges (# of electrons built up) between the 2 points. (Just like heat flow needs a difference in temperatures.) negative positive Electricity always flows from a location with a negative charge to a location with a positive charge. Like charges repel, opposites attract. Remember: Like charges repel, opposites attract. - +
positive (+) negative (-) electrons flow from the bottom to the top Think of a battery, the top has a positive (+) charge and the bottom has a negative (-) charge. So when they are connected, electrons flow from the bottom to the top.
difference in charges voltage The difference in charges between 2 points is called the voltage. same no flow of electrons 2 points can both have a tremendous charge, but if the charge is the same then there will be no flow of electrons between them. - - - - - -
current The number of electrons actually flowing through a conductor is called the current, and is measured in amperes (amps). 1 amp = 6.25 x 10 18 electrons per sec. (6,250,000,000,000,000,000!)
So let’s say that using a voltmeter you determine that there are no electrons flowing from point A to point B through an extension cord connecting the two. Does that mean it is safe for you to touch either of the 2 points? Hmmm……
No! There may be no electrons flowing because the charges are the same. However, your charge may be much different, which would allow the electricity to flow into you.
Electric Currenthigher voltage to lower voltageelectrons lower voltage to higher voltage Electric Current always flows from higher voltage to lower voltage, but electrons in a circuit actually flow from lower voltage to higher voltage. Diagram:
resistors slow flow of electricity Materials called resistors can slow the flow of electricity, without stopping it all together. conductorssmall resistance Almost all materials, even good conductors, provide at least a small amount of resistance to an electric current. ohms Resistance is measured in ohms.
What exactly is a battery?? direct currentchemical reaction A battery is a device which produces a continual direct current, through a chemical reaction.
Batteries can be composed of a liquid electrolyte (a liquid which will conduct an electric current) (wet cell) or a paste electrolyte (dry cell). Whether liquid or paste, the electrolytes are usually acidic. Car and boat batteries are examples of wet cells, flashlight batteries are examples of dry cells.
electrons terminals A chemical reaction inside the battery pulls electrons away from 1 of the terminals and gives them to the other. negative (-) positive (+) This causes 1 terminal to be negative (-) and the other to be positive (+). connected flow of electrons from negative to positive When these terminals are connected through a device, they produce a flow of electrons from negative to positive, which power the device.
Video! How to jumpstart a car. (Saab Ad?) You will be driving soon, and may have to do this on your own. Is this an ad? http://www.youtube.com/watch?v=li1PL6EpFF8 http://www.youtube.com/watch?v=li1PL6EpFF8
circuit A circuit is a pathway along which an electric current can travel, en route to a device. Locating a device along that pathway will allow it to be powered by the electric current. series parallel There are 2 different types of circuits: series and parallel.
1 pathway for electricity to flow stop the flow of electricity A series circuit is one which has only 1 pathway for electricity to flow. All devices are located along this single pathway, and any break in the circuit will stop the flow of electricity. old type Christmas tree lights & flashlights Examples: old type Christmas tree lights & flashlights
How can one faulty bulb cause a whole string of lights to go out? no current flows through the circuit When any part of a series circuit is disconnected, no current flows through the circuit. open circuit This is called an open circuit. The burned-out bulb causes an open circuit in the string of lights.
multiple paths which the electricity can travel down A parallel circuit has multiple paths which the electricity can travel down, with different devices along the different paths. open or broken still carry electricity If one pathways is open or broken, the others can still carry electricity. newer Christmas tree lights, household circuits Example: newer Christmas tree lights, household circuits
current continues to flow When one branch of the circuit is opened, such as when you turn a light off, the current continues to flow through the other branches.
120 V In the United States, the voltage difference in most branches is 120 V. 240 V Some branches used for electric stoves or clothes dryers have a voltage difference of 240 V.
The wiring in a house must allow for the individual use of various appliances and fixtures. parallel circuits This wiring is mostly a combination of parallel circuits connected in an organized and logical network.
main switch circuit breaker fuse box The main switch and circuit breaker or fuse box serve as an electrical headquarters for your home.
wall socketsmajor applianceslights Parallel circuits branch out from the breaker or fuse box to wall sockets, major appliances, and lights.
short circuit current A short circuit occurs when the current stops short of the intended device, usually because of the circuit being completed prior to reaching the device.
fuse circuit breaker To protect against overheating of the wires, all household circuits contain either a fuse or a circuit breaker.
small piece of metalmeltscurrent becomes too high An electrical fuse contains a small piece of metal that melts if the current becomes too high. break in the circuitflow of current When it melts, it causes a break in the circuit, stopping the flow of current.
replace the blown fuse with a new one To enable current to flow again in the circuit, you must replace the blown fuse with a new one. Too many appliances in use at the same time Too many appliances in use at the same time is the most likely cause for the overheating of the circuit.
A circuit breaker is another device that prevents a circuit from overheating and causing a fire. switchautomatically flippedcurrent becomes too great In a circuit breaker, a switch is automatically flipped when the current becomes too great. Flippingcircuit current Flipping the switch opens the circuit and stops the current. pushing switchon Circuit breakers can be reset by pushing the switch back to its “on” position.