Energy Conversion in Electricity – Resistors and Circuits (lesson three of eight)
Grade level(s):Grade 3, Grade 4
Electrical energy can be converted into different forms of energy with a resistor. Electical energy is carried in wires that consist of a single or multiple loop.
resistor, electricity, conduct, series, parallel
What you need:
wires (connectors), bulbs, motors, alligator clips, batteries
whole class, then pairs
Students are introduced to the concept of a resistor and reminded about electrical energy from the previous lesson. They are then challenged to build a GIANT circuit to determine whether the size of a circuit affects whether it lights a bulb. They build as a class a giant series and giant parallel circuit. Then, in pairs, they build their own circuits with different resistors.
Student should be familiar with the different forms of energy and that they can be interconverted.
1) Learn that resistors convert electrical energy into other forms of energy. 2) Learn that a circuit can be as large or small as you want. The important point is it must be a closed to circuit to conduct electricity. 3) Learn that a series circuit consists of one loop, while a parallel circuits consists of two loops.
"Conventional current" is defined as the movement of positive charge. In a copper wire only negative electrons move. Therefore, scientists have defined a term "holes" to describe the positive charges that move in the opposite direction to electrons. A hole is not a physical entity, but rather a learning tool to conceptualize the direction of current flow. Importantly, you can have current flow from both positive and negative ions (e.g. neurological synapses or salt water).
The wires need to be stripped. Check the batteries, lights, and motors to verify that they work properly. Optional: attach alligator clips to the ends of each wire to make it easier for students to connect them.
Lesson Implementation / Outline
5’ Instuctors continue the story: Now that you have learned about the different types of energies and how they can be converted from one energy form to another, one of the scientists in the electricity department of the Exploratorium needs your help lighting exhibits. In particular, he is having trouble making circuits and is tangled in a mess a wires. These smart students decide to further investigate how energy can be converted from one form to another. Students break up into two groups and work with their science partners from last time.
5’ RESISTOR: Describe what a resistor is and how resistors convert electrical energy into different forms of energy. Mention light bulbs, fans, and mechanical motors and different types of resistors. Also mention how resistors are different from conductors and insulators.
10’ GIANT SINGLE CIRCUIT: The class splits into two groups. One instructor takes one group and another the other. Each student is given a large piece of wire. One person in the group is given a light bulb and another a battery. Together, they make a giant single circuit. 10’ GIANT SERIES and PARALLEL CIRCUITS: Now both groups come together and form a giant series circuit. The student with the battery in one of the groups comes out of the circuit. The openings are attached to the other circuit. For a parallel circuit, the openings are attached directly to the other battery. AM and BE emphasize the differences between the circuits (light bulb brightness, what happens to one bulb when the other is unscrewed). 30’ CIRCUIT BUILDING: Now students get their own batteries, light bulbs, and motors and practice making different types of circuits. They can follow a worksheet that challenges them to make a circuit where they can disconnect one light bulb and nothing happens. They can also experiment with adding motors to their circuit or building their circuit with different wires.
Review what happens to light bulb intensity when you make a series circuit (the light bulb dims) and when you make a parallel circuit (no change in light intensity).
Clean up first and then discuss with the class what happened.
Extensions and Reflections
It was difficult for them to connect wires to the batteries and to each other. Alligator clips are essential. Also, many students couldn't see the difference between series and parallel circuits. It may be easier to have a diagram for them to follow. Although, because we did not scaffold the individual time, we got a lot of cool circuits (i.e. two parallel circuits in series).
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