2 Series CircuitA series circuit is a circuit that has only one loop for the current to flow throughSeries circuits are used in flashlight and some Christmas lightsIf any part of the circuit is disconnected, the whole circuit is openWhen on light goes out, they all go out.The current is the same throughout the entire circuitThe total resistance in the circuit is equal to the sum of the individual resistances.
3 Parallel CircuitsWhen you shut of one light in your house, do all the lights go out?No…because houses are wired as parallel circuits not series circuitsParallel circuits contain two or more branches for current to travel throughThe total current in the circuit equals the sum of the currents in its parallel branches.More current will travel through the branches with the least amount of resistance
4 Circuit diagramsElectric circuits, whether simple or complex, can be described in a variety of waysAn easy way to visualize a circuit is by drawing a circuit diagramThere are common symbols used to represent parts of a circuit
7 Household circuitsHousehold circuits are mostly a combination of parallel circuitsThe voltage difference is supplied by the generator at a power plantIn the US, the voltage difference is typically 120VSome appliance require more voltage difference (240V)DryersStovesAs current increases, thermal energy increasesHow do we protect you home from too much thermal energyCoated wiresFusesCircuit breakers
8 Fuses and Circuit breakers The fuse is part of the circuitContain a small piece of metal that melts if the temperature gets too highThe metal melting breaks the circuitMust be replacedPart of the circuitContains a piece of metal that bends when the current is large and too hotCircuit breakers can be reset
9 Electrical PowerElectrical energy is being converted to many different types of energyFanElectricalmechanicalHair dryerElectricalthermalLight bulbElectricallightThe rate at which electrical energy is converted to another form of energy is electrical power
10 Electrical PowerThe electrical power used depends on the voltage difference and the currentElectrical power = current x voltage differenceP = I x VElectrical power is often expressed in kW
11 Let’s try one…The current in an electric clothes dryer is 15 A when it is plugged into a 240V outlet. How much power does the clothes dryer use?3.6 kW
12 Another one…A flashlight bulb uses 2.4 W of power when the current in the bulb is 08 A. What is the voltage difference?3V
13 Electrical energy = electrical power x time Power companies charge by the amount of electrical energy used rather than the electrical power usedElectrical energy is measures in units called kilowatt hours (kWh)Electrical energy = electrical power x timeE = P x t
14 Example 1A microwave oven with a power rating of 1200 W is used for 0.25 h. How much electrical energy is used by the microwave oven?0.30 kWh
15 The Cost of Electrical Energy To determine the cost of electricity you need to calculate the amount of electrical energy used by the energy rate charged by the power company.For example, if a 100 W lightbulb is left on for 5 hours, what is the cost of the electricity if the company charges $0.10 per kWh?First calculate the energy usedThen calculate the cost$0.05
16 Example 2A TV with a power rating of 200 W uses 0.8 kWh in one day. How many hours was the TV used that day?4 hours
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