CONCEPT: Electric current may travel along one or more paths.
CONTENT OBJECTIVE: 4B3.00 To distinguish between parallel and series circuits
INSTRUCTIONAL OBJECTIVES: The learner will:
3.01 recall the definition of an electrical circuit.
3.02 define a series circuit.
3.03 define a parallel circuit.
3.04 distinguish between a parallel and a series circuit.
OUTLINE OF CONTENT:
I. Electrical circuit defined
II. Series circuits
III. Parallel Circuits
IV. Series and Parallel circuits compared
TN COMPONENT OF SCIENCE: Unifying Concepts of Science
TN GOAL:
To enable students to acquire scientific knowledge by applying concepts, theories, principles and laws from life/environmental, physical, and earth/space science.
TN THEME:
2.1 SCALE AND MODEL - The development of models provides a conceptual bridge between the concrete and the abstract, while the use of scales allows for a comparison of differences in magnitude between the model and the desired form.
TN STANDARD(S): The learner will understand that:
2.1d The scale chosen for a model determines its effectiveness.
BENCHMARK: Models should be developed based on scale representations of size, weight, age and speed.
2.1e Different properties are not affected to the same degree by changes in scale; large changes in scale typically change the way things work.
BENCHMARK: Changes made to models represent how real objects or processes are affected by change.
(Have children hold hands in line to form a "series". Make a broken link in the line to show how some will be cut off from the energy source. Lead children to discover that those not connected are not receiving any energy.) Today, we will learn to distinguish between 2 types of circuits, parallel and series.
INSTRUCTION:
An electrical circuit is a path taken by electricity from its source to its destination, and back to its source. A series circuit is an electrical circuit in which the electricity flows from the source through each appliance and returns to the source. There is only one path available for the flow of electricity. It is important to note that the flow of electricity is through each appliance in the order of connection in the circuit. If you follow the instructions given below, you can construct a series circuit.
To make a series circuit you:
1. Strip the insulation from both ends of 3 pieces of wire. You
should see the bare metal.
2. Tape a wire to each end of the battery. The other ends of the wires should not touch while you are making your connections.
3. Connect the battery and sockets. (Draw a diagram of a series circuit on the board.) It is a loop action.
4. Screw the bulbs into both sockets. Record what happens.
5. Loosen one bulb. Record what happens.
6. Tighten the first bulb. Now, loosen the other. Record what happens.
7. Unscrew both bulbs. Disconnect the wires.
A parallel circuit is an electrical circuit in which the electricity flows from the source through each appliance and returns to the source, but more than one path is available for the flow of electricity. It is important to note that the flow of electricity is through each appliance independently and is not dependent on passing through one appliance before passing through a second. (Remember the latter is a requirement of the series circuit.) If you follow the instructions below you can construct a parallel circuit.
To make a parallel circuit you:
1. Strip the insulation from both ends of 2 pieces of wire. Select an additional spot on each wire about two inches from an end and strip away the insulation. You should see the bare metal in each case. (You may elect to use the same wire used to make a series circuit.)
2. Tape a wire to each end of the battery. Use the end of the wire away from the end where the second insulation removal was made. The other ends of the wires and bare spaces should not touch while you are making your connections.
3. Connect the battery and sockets. (Draw a diagram of a parallel circuit on the board.) Each wire should be attached to one of the screws on each socket.
4. Screw the bulbs into both sockets. Record what happens.
5. Loosen the first bulb. Record what happens.
6. Tighten the first bulb. Loosen the second bulb. Record what happens.
In a series circuit, there is only one continuous loop. Current must flow through the loop in order for there to be a circuit. Since electricity passes through both bulbs in a series circuit in order for the circuit to be complete, loosening one bulb disrupts the flow. In a parallel circuit, there are two branches. If a branch is broken, current can still flow through the other one. The most familiar use of bulbs in a series is decorative. Loosening one bulb in some Christmas tree lights extinguishes the entire set. Parallel circuits are used in street lamps so that when one bulb burns out, the others remain lit.
CLOSURE:
Show students 2 mystery sets of lights (one that uses a series and one with a parallel circuit). After displaying what happens when a light is removed from each set, have children distinguish between which set goes with which circuit and give an explanation for the choices.
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