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Entire Activity Download (43 pages - 9 MB) Individual Downloads
Keywords series circuit, simple circuit, current, voltage, resistance, Ohm’s law, amperage, conductivity Key Concepts series circuits, Ohm’s
Law, direct current,
voltage, current,
amperage, insulators,
conductors, multimeter,
ammeter, voltmeter,
ohmmeter, potential Process Skills Utilized Make a hypothesis, Gathering data, Organizing data in a chart form, Analyzing Data, Draw conclusions, Reading a scale on an instrument Intended Grade Level - 6-8 Objectives Using simple electrical components, students will be able to:
Activity Description Part A: Students will be given the components of a simple DC (Direct Current) circuit– wires, buzzer, batteries, battery holder, and switch. By manipulating the different components they will create a simple DC series circuit. Part B: Students will use a multimeter to measure the electrical values of voltage, current and resistance in their newly created circuit. After values are measured and recorded, students will participate in an online Virtual Voltage activity that will help them determine the relationship of voltage to resistance and current in a simple Direct Current (DC) circuit. By participating in this virtual lab they will generate the mathematical relationship called Ohm’s Law. Part C: Using knowledge acquired in previous parts of the activity, students will explore the concept of conductors vs. insulators to determine which materials make the best conductors of electricity. Part D: Using prior knowledge acquired in the previous parts of this activity, students will explore the effects of distance on the resistance of carbon. Carbon is used as an electrode in a common battery and can conduct electricity (although not as well as metals). This activity develops concepts needed to interpret electrical bioimpedance measurements from leg to leg, arm to leg, etc. Part E: Students will determine another factor that affects conductivity by measuring the difference in conductivity between thick pieces of graphite versus a thinner piece of graphite. (Graphite is the carbon used in the lead of a pencil). This activity will help students understand the effect of thickness on electrical conductivity. Activity Materials (per group or station for all parts of this activity–the materials are listed separately for each activity in the Student Data Pages)
Activity Management Suggestions It is strongly advised that each student work through Instruction Cards 2 & 3 (or instructions that come with multimeter) successfully before getting back in the group to do the activity. No student should be allowed to use the multimeter until they know how to use it properly. The Instruction Cards 2 & 3 provided in this activity enable students to understand both how to use the meter and how to read the scales on the top of the face of the meter. A ‘Teacher Answer Sheet’ is provided that has all the answers to the student questions. It is strongly recommended that the teacher read through this ‘Teacher Worksheet’ before students do the lab so that you can guide them as needed. An analog multimeter is used in this activity. This becomes a teaching opportunity to integrate math with science. The Radio Shack 18-Range analog multimeter (Part #22-223) has been selected because of its accessibility and its relatively low cost. If you use the metals provided to test the relationship between distance and resistance, you would find that the metals used would not produce a noticeable difference. Look at the animation found on the following website - it shows what happens to salt when it is placed in water. Salt is an ionic compound. An ionic compound when dissolved in water produces both positive and negative ions. You may also opt to have students look at the animation to help them understand how charged particles are formed when acids, bases, or salts are dissolved in water. http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.html You can choose to use a light bulb with a socket rather than a buzzer. This might cut down on the sound in the room. Make sure the voltage of the bulb is set for slightly more than 3 volts. Students might create a circuit that is not a series but a parallel one therefore it is important that they select one device such as the buzzer or light bulb to test their circuit. Having 10 pieces of the metals, wires and such allows groups to choose their items and then switch with other groups. Students might draw the direction of flow of electrons incorrectly at first (i.e. from positive terminal to negative terminal). That is OK for this part of the lab activity. The diagram needed for Part B showing the placement of the voltmeter and the ammeter is provided - this diagram can be made into a transparency. The voltmeter must be placed across the buzzer, the circuit must be broken, and the ammeter inserted to measure current between the batteries and the buzzer. Remind the student to measure resistance of each component when the battery is NOT connected to the circuit. Five cups need to be prepared for each group. The cups are labeled as follows:
You will probably want to make the solutions a day ahead of time. Make a large batch of salt water. To do this, add 6 heaping teaspoons of salt into a 1000 mL beaker with distilled water. [Kosher Salt is better for this activity since it dissolves easily in water.] Mix until the salt dissolves. For the sugar water, add 5 heaping teaspoons of sugar to a 1000 mL beaker filled with distilled water. Mix until the sugar dissolves. For each group fill a cup half full with each liquid and place a large pat of butter on the bottom of one cup. Extensions Students can be encouraged to learn about series and parallel circuits using multiple sources of resistance (bulbs with sockets, buzzers or other suitable devices.) Look into the historical development of electricity to identify the contributions of the scientists, such a Volta, Ohms, etc. Activity References Used Conductivity of metals Simple series circuits National Renewable Energy Laboratory Public Broadcasting Service – Tesla Inside the Lab Think Quest
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