Exploration of Electrical Circuits
Overview
Total time: 60 mins
Suggested number of students: 20
Objectives: Familiarize participants with basic circuit concepts, such as circuit physics and simple components.
Standards: California Science Standards Physics
5.a. Students know how to predict the voltage or current in simple direct current (DC)
electric circuits constructed from batteries, wires, resistors, and capacitors.
5. c. Students know any resistive element in a DC circuit dissipates energy, which heats
the resistor.
Materials Needed
| Item |
Needed |
| Snap Circuits |
5 |
| Assorted insulators and conductors |
|
Introduction (10)
These snap circuits use building blocks with button snaps to build different electrical and electronic circuits. Each block has a function: there are switches, lamps, batteries, different lengths of wire, etc. You’ll be exploring a variety of these functions and see just how many of the activities you can accomplish.
We’ll do the first project and see what we can learn from the circuit.
Predict what will happen when you close the circuit. What do the components do?
With your finger, trace the path the current will take from the positive terminal to the negative. Note every time it passes something with a resistance like a lamp or a motor, it ends up giving up some energy to light that lamp or move that motor.
Project #1
Note that the two AA batteries provide 3V of electrical “pressure” for the circuit. It is what causes the electrical current to flow from the positive to the negative terminal.
The 2.5V lamp (L1) contains a special wire that glows bright when a large electric current passes through it. Voltages above the bulbs rating can burn out the wire.
The slide switch (S1) is just like a normal switch you come across. It connects or disconnects the wires in a circuit.
Would the circuit differ if we replace the slide switch (S1) with the press switch (S2)?
Simple Circuits (20)
Break up into four or five groups, depending on the number of students, and each group proceeds at their own rate through the projects,
The following are a series of simple circuits that introduce components. While the diagrams are already provided, it’s heavily encouraged that you do the following:
Predict what will happen when you close the circuit. What do the components do?
With your finger, trace the path the current will take from the positive terminal to the negative. Note every time it passes something with a resistance like a lamp or a motor, it ends up giving up some energy to light that lamp or move that motor.
Project #2
The motor (M1) converts electricity into mechanical motion. As you build it, make sure the positive terminal of the motor is correctly wired.
What would happen if I flip the direction of the motor?
What would happen if you replace the 3 wire block with the 2.5V lamp (L1)? Try explaining it in terms of resistance and current. (This is an example of a series circuit. If you trace your finger from the positive to the negative terminal, you HAVE to pass multiple components in “series” before you reach your destination. Unlike a single component who can use up all the energy of a circuit by itself, series components have to share the energy. This results in less energy for everyone.
Project #6
This is an example of a parallel circuit. If you trace the electric path, you find you can take multiple paths to make it to your destination. You can either pass the fan or the lamp. They are not in series.
What would happen to the lamp if we removed the motor? (While the brightness and the motor speed aren’t affected as much as in a series circuit, the battery is draining faster to keep the lamp and motor so bright and so fast.)
Project #7
The resistor (R1) is a component that is specifically designed to “resist” or slow down current flow in a circuit. Remember, all components have varying degrees of resistance, resistors just have a lot more. It is in the circuit to prevent the battery from damaging the LED.
The LED (light emitting diode, D1) is a component that lights up when a circuit is closed.
What would happen if I changed the resistor?
What would happen if I flipped the direction of the LED (D1)?
Project #19
This introduces an integrated circuit. Integrated circuits are used in everything from simple electronic toys to advanced computers. The U1, U2, and U3 are modules containing specialized sound-generation ICs and other supporting components.
The Space War IC (U3) produces a familiar sound effects when properly wired to a speaker.
The speaker (SP) converts electricity into sound. It does this by using the energy of a changing electrical signal to create mechanical vibrations. These vibrations create variations in air pressure which we interpret as sound.
Replace the slide switch (S1) with the photoresistor (RP). How does the photoresistor work?
Electric Circuit Achievements (30)
You did all the Simple Circuit projects!
You made the fan fly in the air!
You made the speakers much quieter as they played the space war sounds!
You created a circuit that ran the LED (D1), lamp (L1), and motor (M1) at the same time!
You created a LED circuit that can be switched on and off, and can run at two different speeds!
You asked about other components and how they work!
Possible follow up questions at the end of class (5)
Explain briefly the difference between a parallel circuit and a series circuit. Draw diagrams of the two circuit connections.
Can an LED be connected with a circuit in any direction? Why or why not? What about a resistor (is there a difference between forward and backwards)?
Sample circuits, predict what will happen when the following components are used to complete the circuit?
