20.3 Electric Circuits Key Concepts What is included in a circuit diagram? How do series and parallel circuits differ? How do you calculate electrical power? What devices make electricity safe to use?

20.3 Electric Circuits To bring electric current into a building, an electrician installs _______________ wires

20.3 Electric Circuits Circuit Diagrams An electric circuit is a complete ___________ through which charge can flow. Circuit diagrams use ________________ to represent parts of a circuit, including a source of electrical energy and devices that are run by the electrical energy. pathway symbols

20.3 Electric Circuits ____________ show the direction of current, from positive to negative. Circuit Diagrams Direction of current Switch Energy source arrows

20.3 Electric Circuits Switches show places where the circuit can be _____________. The circuit diagram also uses a symbol to represent the _________ of energy Neg. terminal = _____ Pos. terminal = _____ Circuit Diagrams Direction of current Switch Energy source opened source -+

20.3 Electric Circuits Series Circuits If one element stops functioning in a series circuit, __________ of the elements can operate. If one element stops functioning in a parallel circuit, the rest of the elements _______________ operate. none still

20.3 Electric Circuits A series circuit has _______ _______ that each charge can follow. Series Circuits onepath

20.3 Electric Circuits A parallel circuit has ________ than one path each charge can follow. Parallel Circuits more

20.3 Electric Circuits Most circuits in a house are _______________. Even if one device stops working, the others will still work. Parallel Circuits parallel

20.3 Electric Circuits The rate at which electrical energy is converted to ________________ form of energy is called ________________ __________. Recall that power is the rate of doing work. The unit of electric power is the joule per second, or ______________(W). Power often is measured in thousands of watts, or ____________________ (kW). Power and Energy Calculations another electricpower watt kilowatts

20.3 Electric Circuits Power and Energy Calculations Electric power can be calculated by multiplying _____________ by ___________. power current voltage currentvoltage

20.3 Electric Circuits Calculating Electric Power An electric oven is connected to a 240-volt line, and it uses 34 amps of current. What is the power used by the oven? power current voltage Power and Energy Calculations P = 34 amps x 240 volts= 8,200 watts

20.3 Electric Circuits An appliance's power rating lets you know how much power it uses under ________________ conditions. Example: An electric stove uses about 6000 watts, and a microwave oven uses about 1000 watts. Power and Energy Calculations normal

20.3 Electric Circuits You can find the electrical energy used by an appliance by multiplying ____________ by __________. Power and Energy Calculations power time

20.3 Electric Circuits The power rating of a typical clothes dryer is 5.4 kilowatts. If you use the clothes dryer for 2 hours, what is the energy use? Power and Energy Calculations E = 5.4 kilowatts x 2 hours = 10.8 kilowatt-hours

20.3 Electric Circuits Electric power companies usually determine charges on your electric bill using _________________. A kilowatt-hour equals 3,600,000 joules. Kilowatt-hours

20.3 Electric Circuits Most household circuits usually have an average voltage of 120 volts. Each device that is turned on _________________ the current. If the current exceeds the circuit’s safety limit, the wire may _________________. Electrical Safety increases overheat

20.3 Electric Circuits Electrical Safety Several methods or devices help make electrical energy safe to use… _______________ wiring ______________ circuit ________________ _____________________ _______________ plugs correct fuses breakers insulation grounded

20.3 Electric Circuits Fuses have an internal wire that ________ if a current is too great….prevents current overload. Home Safety “Blowing a fuse” melts

20.3 Electric Circuits A circuit breaker is a switch that _______________ when current in a circuit is too high…prevents current overload. The circuit breaker must be reset before the circuit can be used again. Home Safety opens

20.3 Electric Circuits Personal Safety Electrical wiring in a home is _________________ to protect people. If the insulation is damaged, you may accidentally touch the bare wire and get a _____________. Avoid touching electrical devices with ___________ hands, because your hands conduct current more readily when they are wet. insulated shock wet

20.3 Electric Circuits Insulation also prevents ___________ circuits… when a current finds a short path through a circuit with ____________ resistance. A ____________-prong plug can prevent shocks caused by short circuits. If a short circuit develops, the current takes an easier path to the _____________through the grounding wire instead of your body! short less three ground

20.3 Electric Circuits The transfer of excess charge through a conductor to Earth is called _________________ Even a small current in your body can cause a painful shock or injury. Electrical Safety grounding

20.3 Electric Circuits Assessment Questions 1. A number of light bulbs are connected to an energy source in a series circuit. What will happen to the other bulbs if one of the bulbs burns out? a.Nothing will happen. b.They will be brighter. c.They will be dimmer. d.They will turn off.

20.3 Electric Circuits Assessment Questions 2.A pair of computer speakers are connected to a 12-volt power supply with a current of 1.25 amps running through them. What is the electric power? a.0.8 watt b.1.25 watt c.12.5 watt d.15 watt

20.3 Electric Circuits Assessment Questions 3. A fuse has a switch that opens to prevent overheating when the current in a circuit is too high. True False