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Transcript
Electricity Hands-On #1 – Assembling Circuits Create a Series Circuit Series Circuit items Draw circuit with symbols Signature of teacher Brightness of bulb #1 with switch open Brightness of bulb #1 with switch closed One light bulb, one battery, one switch (Fig. 1) Two light bulbs, one battery, one switch Two light bulbs, two batteries, one switch Explain what happens when you move up and down the resistor. Two batteries, one light, one switch, variable resistor (Fig. 2) Summary statement about series circuits: ______________________________________________ ________________________________________________________________________________ Fig. 1 Fig. 2 Page 1 Where might variable resistors be used? ___________________ Create a Parallel Parallel Circuit items Circuit Draw circuit with symbols Signature of teacher Brightness of bulb #1 with switch closed Brightness of bulb #2 with switch closed Two light bulbs, one battery, one switch (Fig. 3) Two light bulbs, two batteries, one switch Two light bulbs, two batteries, two switches Summary Statement about parallel circuits: _____________________________________________ ________________________________________________________________________________ Reread p.610 to help you . . . Compare and contrast series and parallel Circuits: Similarities: Differences: Advantages/Disadvantages: Fig. 3 Page 2 Electricity Hands-On #2 – What is a Current? Using a Galvanometer Construct the circuit and then position the compass as shown in the drawing. Close the switch and observe the needle of the compass. Open the switch and observe the needle. Move the compass to different spots around and inside the coil. Each time, observe which end of the needle points toward the coil when you close and then open the switch. Record your observations. Observations: ____________________________________________________________ Compass ________________________________________________________________________ ________________________________________________________________________ Teacher Signature ___________________ Construct the galvanometer circuit as shown in the drawing below. To help balance the pointer, stick the paper clip on top of the magnet. Move the clip to the left or right a little at a time until the pointer balances straight up and down on the 0 line. Observe what happens as you close and open the switch. Record your observations: _______________________________________________________________________ Now look at the circuit diagram of the galvanometer circuit. Identify the battery and the switch. The remaining part of the circuit are represented by the G symbol. Draw the circuit diagram with the switch, battery, and galvanometer: _____________________________________ Read the textbook pp. 636-638. In your own words, explain how a galvanometer works and give 2 practical uses: Explain what the Galvanometer measures: * Stop here until the demonstration ** Page 3 Do not continue until you have seen the demonstration Electricity Hands-On #3 – Voltage and Amperage Using a Digital Multimeter (DMM) Measuring Volts (force): Batteries store energy. This energy is rated in Volts. 1 volt = 1 Joule per Coulomb of charge in the battery. If a battery has a charge of 6 volts, each Coulomb of charge has 6 Joules of energy. Using your textbook p. 414, a Joule is a unit of ___________ which is __________x__________. How many volts are in your battery? ________ So, how many Joules of energy does each Coulomb of electrons produce? _________ Voltage must be measured around a load. This means the circuit will be built, and then the multimeter will be place with one wire on one side of the load, and the other wire on the other side of the load. The circuit does NOT have to be taken apart to measure the force. Draw and build a series circuit with 1 battery, 1 switch, 1 light, and 1 voltmeter measuring the voltage of the light bulb. Drawing of circuit Teacher signature. V = __________ Measuring Amps (speed of current or flow of electric charge): Energy must travel out of the battery, through the load, and back to the battery. The speed at which this happens is the Current, measured in Amps. 1 Amp = 1 Coulomb/second Reread pp.600-601 and fill in the blanks: A coulomb = _____________ electrons. Lightning produces ______________ coulombs. A flash camera uses about ________________ coulombs for a flash. Amperage must be measured with an ammeter in series, just behind a load. Therefore the circuit must be broken and the DMM placed into the circuit to read amps. Draw and build a series circuit with 1 battery, 1 switch, 1 light, and an Ammeter, measuring the current just behind the light bulb. Drawing of circuit Teacher signature. Amps = _________ Using Ohm’s Law (see p. 607), determine if your measurements on this page work. Show math: Page 4 Electricity Hands-On #4 – Voltage and Amperage Series To measure the voltage (V) the meter must be placed around the load. Measuring amps (I) must be done in series behind a load. Use this diagram for each test Load being tested Voltage Teacher Signature VB VB V1 V1 V2 V3 V2 V3 + V2 + V3 = _____________ volts Is this answer close to VB ? _______ V1 IB I2 Current being tested Amps Teacher Signature IB I1 I1 I2 What do you notice about all of the amps? _________________________________ _________________________________ A total of _______ Volts leaves the battery. All of the energy is used up as it moves through the circuit, so VB = V1 +_ V2 + V3 Page 5 Electrons only have one path to flow in a series circuit, therefore if one flows fast, the rest have to flow fast. If one flows slow, the rest must flow slow. Therefore, current is constant. I B = I 1= I 2 Electricity Hands-On #4 – Voltage and Amperage Parallel To measure the voltage the meter must be placed around the load. Measuring amps must be done in series behind a load. Load Being Tested VB Volts Use this diagram for each test Teacher Signature VB V1 V1 V2 V2 What do you notice about all of the Volts? ___________ ______________________________________________ Current being tested Amps Teacher Signature IB(out) IB (out) IB(in) IB (in) I1 I1 I2 I2 I1 When in parallel, both paths get equal amount of energy (Joules per Coulomb) VB = V1 = V2 Show math: Page 6 + I2 = ______________ . Is this close to IB ? ______ If the flow of electrons splits in to two paths, each path has less flow. When the paths meet back together the flow becomes full again. Show Work: IB (out) = IB (in) IB = I1 + I2 Electricity Hands-On #5 –Amperage with Parallel Batteries Complete the following circuit and determine the appropriate Amperage for each. Use a Christmas bulb light for the R **Notice – all 3 set-ups are the same except for where the ammeter is placed + A + A R R + - + - B B Circuit A Circuit C A R B Teacher Signature Circuit B Current Switch Setting Switch A Switch B Closed Open Open Closed Closed Closed Circuit A Ammeter Reading Circuit B Circuit C What is the Ammeter reading current of in A? ___________________________ What is the Ammeter reading current of in B? ___________________________ What is the Ammeter reading current of in C? ___________________________ Page 7 Electricity Hands-On #6 – Creating a Motor Before connecting the last wire, set up the circuit as shown and make sure the coil is balanced and free to spin. Keep the circuit open and flick the coil with your fingertip to start it spinning. Record what happens in the data table below. Close the circuit and again flick the coil. Again record observations. Draw the circuit Teacher Signature Open Circuit Observations Closed Circuit Observations Use the multimeter to measure amps and volts. Use Ohm’s Law to calculate the resistance of the motor. Show work: Amps = ______ Volts = ______ Resistance = ________________ Indicate the charges placed on the coil of wire when a current is passing through it? (Remember Lab #2 with the Galvanometer). The magnet is placed below it. Indicate the charge on the magnet if the coil is trying to push away from it. Page 8 Electricity Lab Pack Circuits Name: Period: