Presentation on theme: "Circuit A complete path of conductors from the"— Presentation transcript:
1 Circuit A complete path of conductors from the negative terminal of thevoltage source back tothe positive terminal of thevoltage source.Two main types of circuits:SeriesParallelWhat’s wrong in this picture???
2 What is a circuit?Would the light bulb still light up if the filament were broken? No!The electrons must have a complete circuit to flow through.A circuit is any path along which electrons can flow.For the continuous flow of electrons, there must be a complete circuit with no gaps
3 CircuitsSeriesOne path. All current flows through all parts of the circuit.“All or nothing”If there is a break in the circuit, open circuit, no current will flow.ParallelMore than one path. Current splits and travels through different paths.“Selective”If there is a break in one branch of the circuit, current can still flow through other branches.What’s wrong in this picture???
4 Circuit Elements We have already talked about some properties of an electrical circuit…Current, which is the flow of electrons.Resistance, which is the slowing of electrons.Voltage, which produces the flow of electrons.These properties have different parts of acircuit, or circuit elements.
5 Series Circuits When items are connected in series, they provide one single path for the current to flow through For example, when the current travels out ofthe wall, through the filament, and back into the wall, the light bulb has been connected inseries
6 Series Circuits There are four important characteristics of a 1. Current has a single pathway through the circuit, socurrent through each device is the same.2. Current is resisted by the first device, then the second,then the third and so on, so the total resistance is thesum of the individual resistances
7 3. The current in the circuit is equal to the voltage from the voltage source divided by thetotal resistance in the circuit (Ohm’s Law,duh!)4. Ohm’s Law applies separately to each device,so the voltage drops across each device,according to its resistance
8 Series Circuits Series circuits have some pretty obvious disadvantages If several light bulbs are connected in series, and one goes out, what happens to the circuit?This idea may be familiar toyou through some traumatizing Christmas-tree decorating experience.
9 Parallel Circuit When items are connected in parallel, they form separatebranches, any one ofwhich the electronscan flow through.In a parallel circuit, allof the electrons DONOT flow through allof the circuitelements
10 Parallel CircuitThere are four important characteristics of parallel circuits:1. Each device connects the same two points in a circuit, so the voltage is the same across each device.2. The total current in the circuit splits up among the different branches (think of the electrons getting to chose which branch they go down), so the current is different across each branch. More current passes through the branches with lower resistance (Ohm’sLaw)
11 Parallel CircuitThe total current in the circuit equals the sum of the currents in its parallel branches.4. As the number of parallel branches increases,the total resistance decreases.Think of checking out at the grocery store. A certain number of people need to check out (like electrons in a circuit). As more check-out lanes open, the people can move through more quickly.Thus as the number of lanes increases, the“resistance” decrease.
12 Review and Compare Series Parallel All electrons pass through single pathVoltage drops different across each deviceCurrent is the samethrough each deviceParallelElectrons pass throughone of many pathsVoltage is the sameacross each deviceCurrent is differentthrough each device
13 Current through a conductor is proportional to the applied voltage Ohm’s LawCurrent through a conductor is proportional to the applied voltageConductor is also known as a resistorAn ideal conductor is a material whose resistance does not change with temperatureV = Voltage (Volts = V)I = Current (Amperes = A)R = Resistance (Ohms = Ω)
14 Current and Voltage Defined Current: (the current in electrical circuits)Flow of current from positive terminal to the negative terminal.- has units of Amperes (A) and is measured using ammeters.Voltage:Energy required to move a charge from one point to another.- has units of Volts (V) and is measured using voltmeters.Think of voltage as what pushes the electrons along in the circuit, and current as a group of electrons that are constantly trying to reach a state of equilibrium.
16 Ohm’s Law continuedThe total resistance of a circuit is dependant on the number of resistors in the circuit and their configurationSeries CircuitParallel Circuit
17 CircuitsSeriesEach resistor added decreases the voltage. (Loads share the current.)RT = R1 + R2 +R3…As resistors are added, total resistance increases.ParallelEach resistor gets full voltage. (Each load draws own current.)1/RT = 1/R1 + 1/R2…As resistors are added, total resistance decreases.
18 Fuses & Circuit Breakers Limit the current that runs through wires in your houseThese wires have some resistanceEnergy loss by I2R converts to heatHot wires can start a fireLimit the current with a fuse or circuit breaker