Teaching Parallel Circuits to Your Students

Parallel Circuits

To start, we need to define current and voltage:

  • Current is the rate (or speed) at which the electrons are flowing through the circuit and is measured in amperes (Amps).
  • Voltage is technically the electrical potential difference between the beginning and end of a circuit….or simply, the force at which the current travels through the circuit. Voltage is measured in Volts (joules/coulomb).

We are going to start with the simple circuit we created in a previous post (connect the alligator clip to negative side of battery, then connect to knife switch, knife switch to lamp holder, lamp holder to positive side of battery).

Now let’s make some modifications and create a parallel circuit. In a parallel circuit, the voltage stays constant in each branch of the circuit.

Creating a Parallel Circuit

Using our simple circuit with the knife switch in the upright position, we are going to add another load (light) and create a parallel circuit.

  1. Take a wire with alligator clips and attach to one side of the existing lamp holder.
  2. Using a separate wire, attach one end to the other side of the existing lamp holder (*note: there will be 2 clips attached to each side of the existing lamp holder).
  3. Take the ends of the two wires that are free and clip one to each side of a new lamp holder with light bulb. When the knife switch is closed, both lights illuminate.

In a parallel circuit, the voltage stays constant in each branch of the circuit. So, using a 1.5V battery, both bulbs are receiving 1.5V of electricity. This is the reason both light bulbs have the same brightness. If you measured the current, you will find that the current is divided into each branch. Therefore, if 10 amps of current were flowing through the circuit, each light (or branch of the parallel circuit) would be receiving 5 amps of electricity. Adding the amount of current in each branch together, will give the total amount of current introduced into the circuit.

Now you’re well equipped to teach your students all about parallel circuits. Amazon has a many experiments to teach and explain how circuits work. Check out Energy Ball and Energy Stick.

Steps to a Successful Science Fair Project

Science fair project

8 steps to a successful science fair project. Photo by terren.

  • Did the student learn something from the project?
  • Did the student follow the scientific method to complete the experiment?

If the answer to each these questions is yes, then the student was successful. Let me give you 8 steps to a Successful Science Fair Project.

  1. The first and most important step is the Selection of a Topic. The topic should be of interest to the student and selected prior to designing the science fair project. Example topics could include oceanography, basketball, ballet, sharks, micro-organisms, magnets, etc.
  2. The second step involves some creativity. At this point, you must ask a question about your topic that can be answered in an experiment. For example, if the topic was micro-organisms, the question might be, “What surface in my house contains the most bacteria?”
  3. Next, you must research the topic and discover background information that will be useful for your experiment. In order to answer the question above, you would need to know how to grow bacteria, how to take samples, optimum growth temperature, safety procedures, where do bacteria grow, etc.
  4. Then, you need to take the question from step 2 and reword it, so that, a purpose statement is created. From the question we created in step 2, our purpose statement could be, “The purpose of my experiment is to determine which surface in my home contains the most bacteria.”
  5. Now take the purpose of your experiment and develop a hypothesis. The hypothesis is an educated guess as to the outcome of your experiment. Your hypothesis could be, “My hypothesis is that the toilet seat has the most bacteria.” Don’t ever change your hypothesis. Your hypothesis is based on your research and knowledge. If the experiment disproves your hypothesis, that is OK. An incorrect hypothesis does not make an unsuccessful project.
  6. Design the experiment. This is where most people start. Never start with the experiment, because many times the outcome is know. Learning and using the scientific method is the most important part. During this step, you will determine the materials needed, explain the procedure, collect data and record results.
  7. Draw a conclusion. The conclusion is simply, “Was my hypothesis correct or incorrect?” Your conclusion might be, “In conclusion, my hypothesis was incorrect, the kitchen sink was actually the area that contained the most bacteria.”
  8. The final step is to make an attractive science fair display. You should have label headings, such as, Purpose, Hypothesis, Materials, Procedure, Data/Results, Conclusion. Display part of your experiment. If parts of the experiment are not able to be displayed, use photos that explain your procedure and results.

Teaching Electricity and Simple Circuits to Elementary Students

Circuits in the elementary classroom

Teaching circuits to students

Electricity can be a complex and imposing topic to present to your students. Before we talk about circuits, let’s go over a few definitions:

  • Load - A device that does work or performs a job (i.e., the light bulb in our circuit).
  • Electrical current - The flow of electrons from an area of high concentration (“a lot”) to an area of lower concentration. *Note: the negative side of the battery has a high concentration of electrons.
  • Electron - A negatively charged particle that orbits the nucleus of an atom.
  • Generator - A device that converts mechanical or chemical energy into electricity. Wind, water or an engine can power a generator.
  • Electrical circuit - An electrical path that is closed (all parts connected), allowing the electricity to return to the original source (the battery).
  • Parallel Circuit - A circuit in which the components are connected like a ladder. This circuit splits the voltage equally to all of the components.

Simple Circuit

Creating a Simple Circuit

  1. Place a “D” cell battery in a battery holder. The battery holder will allow you to attach wires with alligator clips to the positive and negative ends of the battery.
  2. Now, screw a small light bulb (mini lamp) into a lamp holder. Like the battery holder, the lamp holder will allow you to attach alligator clips to the light bulb (your load).
  3. To complete the circuit, you will need two wires with alligator clips. Use one wire to connect the negative side of the battery to the lamp holder. It does not matter which side of the lamp holder the wire is attached. Connect the positive side of the battery to the lamp holder using the second wire. This wire will attach to the opposite side of the lamp holder. The light bulb should be lit.

Remember, the voltage of the battery and light bulb should be similar. If the battery voltage is too much larger than the voltage capacity of your bulb, the bulb will burn out. A “D” cell battery provides 1.5V.

Simple Circuit with Switch

Adding a Knife Switch to a Simple Circuit

We will modify our simple circuit described above to complete this task.

  1. Disconnect the alligator clip that is attached to the negative side of the battery and re-connect it to one side of the knife switch. Make sure the knife switch is in the upright position.
  2. Take a separate wire and connect the negative side of the battery to the knife switch. Notice that the light is off.
  3. Lower the arm on the knife switch to connect the circuit and light the bulb.

The knife switch allows you to discuss breaking the circuit and stopping the flow of electrons.

Heath Scientific provides a kit called “Making Circuits Simple” that includes all of the components described in this article. It’s an easy, all-in-one kit to demonstrate circuits to your students.

Motility in Bacteria (Prokaryotes)

flagella on bacteria

Flagella on bacteria by Mike Jones

Many types of bacteria have the ability to move. Movement in microorganisms allows them to locate food and to remove themselves from toxic micro-environments and less than desirable temperature conditions. Bacteria expend a large amount of energy during this process.

Bacteria use appendages called flagella to move. Flagella are composed of protein subunits called flagellin. Flagella can be located at one or both ends of a bacteria (polar flagellation) or spaced over the entire surface of the cell (peritrichous flagellation).

The appendages are not straight, but helical shaped (like a wave). The flagella for each species of bacteria have a constant wavelength (the distance between each wave in the flagella).

Unlike the human hair, a flagellum grows from the tip, not the base. Flagellin protein is made in the cell and transported through a hollow center to the tip of the flagellum. Therefore, if a tip is broke off, a new one is regenerated. The flagella are stiff structures and move only at the base, like a propeller.

The average speed of a bacteria is 50 micrometers per second. If the bacteria were the size of a cheetah, it would move at about 30 miles an hour.

The Effects of Temperature on Water Absorption in Warblettes

In this experiment, we are going to determine the effect of temperature on water absorption in warblettes.

To complete this experiment, you will need the following:

Procedure

1. Create an ice bath by placing a mixture of water and ice in the 500 ml beaker. Fill approximately 1/2 full.

2. Using a graduated cylinder, pour 50 ml of water into one of the 250 ml beakers. Place the beaker in the ice bath. This will keep the water cold during the experiment. For the purpose of this experiment, it will not be necessary to measure the actual temperature of the water. Our main goal is to compare cold and warm temperatures in general. The water will drop to between 5 and 10 degrees celsius.

3. Using a 50 ml cylinder, add 50 ml of hot tap water to the second 250 ml beaker. The water temperature will be approximately 40 degrees C and will continually cool during the experiment.

4. Add 40 Warblettes to each of the 250 ml beakers. Allow the Warblettes to absorb water for 20 minutes.

5. Take one beaker and pour the remaining water into the graduated cylinder. Measure this amount and subtract from the original 50 ml. This calculation will give you the amount of water absorbed by the Warblettes. Repeat this step for the second beaker.

Result

The warmer temperature water will promote faster growth of the polymer. Compare this to real life applications like:

  • Coffee, tea, sugar, and other solids dissolve faster in hot water.
  • Most bacteria grow best at warmer temperatures (close to human body temperature).
  • Ice on a contusion reduces bruising by slowing blood flow.

Warblettes can be used in many experiments and create interest and excitement while reinforcing scientific principles.