11.4 Electric Circuits *Identify parts of a circuit *Trace the path of electrons through two types of circuits *Compare series and parallel circuits *Predict how circuits are wired in a home

Electrical Circuits What is a circuit? Suppose you took off for a walk on a path in the park and after making several twists and turns you ended your trip at the same place you started but never once did you back track or retrace your path. If you made this trip you would have com- pleted a circuit. A pathway that ends where it started.

Let’s imagine that along your trip you came upon a bridge over a very deep gorge that had been washed away by a recent storm. Could you continue on your walk? Why? Electrons trying to move along their path through an electrical circuit act just like people on a path through the park. As long as they have a pathway to travel they will do so but this pathway must lead them back to where they started.

ELECTRICAL CIRCUITS Electrons flow through a closed, continuous path called a CIRCUIT. ENERGY SOURCE - SWITCH (breaker) + TAKS

Parts of an Electrical Circuit + - Battery -e source Wires -e pathway Switch to close the circuit Resistance things which the -e make work. clock light bulb

Parts of the circuit defined Dry cell The dry cell or battery provides a source of electrons ( in other places these may come from a power gene- rating plant.) Wires provide the pathway for electrons to follow and find their way back to the battery. The switch, when opened, prevents electrons from flowing, when closed provides a closed circuit for the electrons to find their way to the resistance and back to the battery.

Parts of a circuit defined Resistance is any type of object which requires electrical energy to operate. You guys getting the picture?

Types of Circuits Series Circuit - + What do you notice about the series circuit and how electrons would flow? What would happen if one of the light bulbs burned out? Would the others continue to work? No this would open the path that the electrons need to get back to the battery. Some Christmas tree lights are wired in a series circuit.

Types of Circuits (continued) Parallel Circuits Dry cell In a parallel circuit each part of the circuit provides the electrons with a pathway to get back to the source even if one of the others goes out. The wiring in our homes is in parallel circuits. If one light bulb goes out in your house, everything else still works.

Electric Power and Safety Electric Power You should remember that power is the rate at which work is done. So, what is electrical power? If you said that it is the rate that electricity does work you are correct. I remember hearing about that.

Calculating Electric Power Power (P) Voltage (V) current (I) P = V x I An automobile headlight draws 30 amps from a 12 V battery. How much power does it use? P = V x I P = 12V x 30 A P = 360 W The watt (W) is the unit for electrical power. 1W = 1 joule / second

Practice Problems What is the power of a fan operating at 120 V and 3 amps? P = V x I P = 120 V x 3 A P = 360 W

Calculating Electrical Energy Energy (E) Power (P) time (t) E = P x t How much energy is required to operate the head light in the first practice problem for 3 hours? E = P x t E = 360 W x 3 hrs E = 1080 Wh or 1.08 kWh (kilowatt hours)

Practice Problem How much energy would the fan from power problem #2 require if it were operated for 5h? E = P x t E = 360 W x 5 h E = 1800 Wh or 1.8 kWh

Electrical Safety 1. You cannot see it - it will kill you dead ! ! ! 2. Ground wires should be on appliances to prevent shock from outside the appliance. That is what the third prong on the plug is. 3. Broken wires should be replaced and appliances with broken wires should not be used. 4. Electrical appliances should not be used near water. Water can conduct electricity.

Safety (continued) 5. Do not overload circuits by adding too many appliances to one plug or cord. 6. Fuses and circuit breakers should be used to prevent overloads. Do not use fuses above the recommended amps in circuits.

A few Quiz Questions 1. T or F In order for electricity to flow through a circuit, the circuit must be open. 2. A _______________is used to open or close a circuit. 3. In a ___________ circuit the electrons have only one path to get back to their source. 4. Name a common part of a circuit that is resistance. 5. The rate at which electricity does work is called _____________ ___________. 6. T or F Overloading a circuit may cause a fire. 7. ___________ or ____________ are used to prevent overloads. 8. ___________ wires are used to prevent electric shock. 9. T or F A battery is a source of electricity. 11 points each

A few Quiz Questions 1. T or F In order for electricity to flow through a circuit, the circuit must be open. 2. A _______________is used to open or close a circuit. 3. In a ___________ circuit the electrons have only one path to get back to their source. 4. Name a common part of a circuit that is resistance. 5. The rate at which electricity does work is called _____________ ___________. 6. T or F Overloading a circuit may cause a fire. 7. ___________ or ____________ are used to prevent overloads. 8. ___________ wires are used to prevent electric shock. 9. T or F A battery is a source of electricity. switch series electric power Fuses breakers Ground 11 points each

Now that you have the pieces of the electricity puzzle The End