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Activities involving basic understanding of electricity, magnetism and simple electrical devices. Hopefully this will involve test type questions and.

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Presentation on theme: "Activities involving basic understanding of electricity, magnetism and simple electrical devices. Hopefully this will involve test type questions and."— Presentation transcript:

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2 Activities involving basic understanding of electricity, magnetism and simple electrical devices. Hopefully this will involve test type questions and hands-on activities. Could be: stations. building specific circuits. analyzing circuits. analyzing graphs. mapping fields. there are many possibilities. Could be: stations. building specific circuits. analyzing circuits. analyzing graphs. mapping fields. there are many possibilities.

3 Series Circuit In a series circuit the Equivalent Resistance is the sum of the individual resistances. Series Circuit In a series circuit the Equivalent Resistance is the sum of the individual resistances. R 3 = 6.0 Ω R 1 = 4.0 Ω R 2 = 8.0 Ω R S = R 1 + R 2 + R 3 = = 18.0 Ω A quick check is the Equivalent Resistance for resistors in Series is always more than the largest individual resistance. In the above example, R S must be greater than 8.0 Ω. A quick check is the Equivalent Resistance for resistors in Series is always more than the largest individual resistance. In the above example, R S must be greater than 8.0 Ω.

4 Parallel Circuit In a parallel circuit the Equivalent Resistance is the reciprocal of the sum of the reciprocal of the individual resistances. Parallel Circuit In a parallel circuit the Equivalent Resistance is the reciprocal of the sum of the reciprocal of the individual resistances. 1/R P = 1/R 1 + 1/R 2 + 1/R 3 1/R P = 1/ /8.0 +1/6.0 1/R P = 13/24 Ω 1/R P = 1/R 1 + 1/R 2 + 1/R 3 1/R P = 1/ /8.0 +1/6.0 1/R P = 13/24 Ω A quick check is the Equivalent Resistance for resistors in Parallel is always less than the smallest individual resistance. In this case R P must be less than 4.0 Ω. A quick check is the Equivalent Resistance for resistors in Parallel is always less than the smallest individual resistance. In this case R P must be less than 4.0 Ω. R P = 24/13 Ω = 1.85 Ω R 3 = 6.0 Ω R 1 = 4.0 Ω R 2 = 8.0 Ω Using your calculator: R P = (R R R 3 -1 ) -1 = ( ) -1 = 1.85 Ω Using your calculator: R P = (R R R 3 -1 ) -1 = ( ) -1 = 1.85 Ω

5 Using the circuit shown below, what is the current passing through each resistor? R S1 = R 2 + R 3 = 6.20 Ω Ω = 16.0 Ω R S2 = R 4 + R 5 = 16.0 Ω Ω = 24.0 Ω R S1 = R 2 + R 3 = 6.20 Ω Ω = 16.0 Ω R S2 = R 4 + R 5 = 16.0 Ω Ω = 24.0 Ω R 1 = 5.40 Ω 30.0 V R S2 = 24.0 Ω R S1 = 16.0 Ω R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω In analyzing circuits, you can replace any group of resistors with its equivalent.

6 Using the circuit shown below, what is the current passing through each resistor? 1/R P = 1/R S1 + R S2 1/R P = 1/ /24.0 = 5/48.0 R P = 48.0/5 = 9.60 Ω 1/R P = 1/R S1 + R S2 1/R P = 1/ /24.0 = 5/48.0 R P = 48.0/5 = 9.60 Ω R 1 = 5.40 Ω 30.0 V R S2 = 24.0 Ω R S1 = 16.0 Ω R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω R 1 = 5.40 Ω 30.0 V R P =9.60 Ω

7 Using the circuit shown below, what is the current passing through each resistor? R TS = R P + R 1 R TS = 5.40 Ω Ω = 15.0 Ω I S = I 1 = I P = V S /R TS = (30.0 V)/(15.0 Ω) I S = I 1 = I P = 2.00 A R TS = R P + R 1 R TS = 5.40 Ω Ω = 15.0 Ω I S = I 1 = I P = V S /R TS = (30.0 V)/(15.0 Ω) I S = I 1 = I P = 2.00 A R 1 = 5.40 Ω 30.0 V R S2 = 24.0 Ω R S1 = 16.0 Ω R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω R 1 = 5.40 Ω 30.0 V R P =9.60 Ω

8 Using the circuit shown below, what is the current passing through each resistor? V P = I P R P = (2.00 A)(9.60 Ω) = 19.2 V V S1 = V S2 = V P = 19.2 V I 4 = I 5 = V S2 /R S2 = 19.2 V/24.0 Ω I 4 = I 5 = 0.80 A V P = I P R P = (2.00 A)(9.60 Ω) = 19.2 V V S1 = V S2 = V P = 19.2 V I 4 = I 5 = V S2 /R S2 = 19.2 V/24.0 Ω I 4 = I 5 = 0.80 A R 1 = 5.40 Ω 30.0 V R S2 = 24.0 Ω R S1 = 16.0 Ω R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω R 1 = 5.40 Ω 30.0 V R P =9.60 Ω

9 Using the circuit shown below, what is the current passing through each resistor? V P = I P R P = (2.00 A)(9.60 Ω) = 19.2 V V S1 = V S2 = V P = 19.2 V I 2 = I 3 = V S1 /R S1 = 19.2 V/16.0 Ω I 2 = I 3 = 1.20 A V P = I P R P = (2.00 A)(9.60 Ω) = 19.2 V V S1 = V S2 = V P = 19.2 V I 2 = I 3 = V S1 /R S1 = 19.2 V/16.0 Ω I 2 = I 3 = 1.20 A R 1 = 5.40 Ω 30.0 V R S2 = 24.0 Ω R S1 = 16.0 Ω R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω R 1 = 5.40 Ω 30.0 V R P =9.60 Ω

10 Using the circuit shown below, what is the voltage drop across each resistor? V 1 = I 1 R 1 = (2.00 A)(5.40 Ω) = 10.8 V V 2 = I 2 R 2 = (1.20 A)(6.20 Ω) = 7.44 V V 3 = I 3 R 3 = (1.20 A)(9.80 Ω) = V V 4 = I 4 R 4 = (0.8 A)(16.0 Ω) = 12.8 V V 5 = I 5 R 15 = (0.8 A)(8.00 Ω) = 6.4 V V 1 = I 1 R 1 = (2.00 A)(5.40 Ω) = 10.8 V V 2 = I 2 R 2 = (1.20 A)(6.20 Ω) = 7.44 V V 3 = I 3 R 3 = (1.20 A)(9.80 Ω) = V V 4 = I 4 R 4 = (0.8 A)(16.0 Ω) = 12.8 V V 5 = I 5 R 15 = (0.8 A)(8.00 Ω) = 6.4 V R 1 = 5.40 Ω 30.0 V R 2 = 6.20 Ω R 3 = 9.80 Ω R 4 = 16.0 Ω R 5 = 8.00 Ω I 1 = 2.0 A I 2 = I 3 = 1.2 A I 4 = I 5 = 0.8 A I 1 = 2.0 A I 2 = I 3 = 1.2 A I 4 = I 5 = 0.8 A

11 Working with circuits. The challenge here is to be able to apply the basic concepts to a setup in the lab. Either an existing one or have you build a given circuit. There are many ways to achieve this. Here are some examples that were used at Nationals. Working with circuits. The challenge here is to be able to apply the basic concepts to a setup in the lab. Either an existing one or have you build a given circuit. There are many ways to achieve this. Here are some examples that were used at Nationals.

12 Before you is a circuit with switches, identical light bulbs and a battery holder. Draw a schematic of the circuit as if the following were true. There are batteries in both holders that were wired properly in series. There is a voltmeter placed to measure the voltage drop across Bulb #1. There is an ammeter placed to measure the current passing through just bulb #1. There is an ammeter placed to measure the current passing through just bulb #3. Before you is a circuit with switches, identical light bulbs and a battery holder. Draw a schematic of the circuit as if the following were true. There are batteries in both holders that were wired properly in series. There is a voltmeter placed to measure the voltage drop across Bulb #1. There is an ammeter placed to measure the current passing through just bulb #1. There is an ammeter placed to measure the current passing through just bulb #3.

13 Bulb #1 Bulb #2 Switch #1 Bulb #3 Switch #2 Before you is a circuit with switches, identical light bulbs and a battery holder. Draw a schematic of the circuit as if the following were true. There are batteries in both holders that were wired properly in series. There is a voltmeter placed to measure the voltage drop across Bulb #1. There is an ammeter placed to measure the current passing through just bulb #1. There is an ammeter placed to measure the current passing through just bulb #3. Before you is a circuit with switches, identical light bulbs and a battery holder. Draw a schematic of the circuit as if the following were true. There are batteries in both holders that were wired properly in series. There is a voltmeter placed to measure the voltage drop across Bulb #1. There is an ammeter placed to measure the current passing through just bulb #1. There is an ammeter placed to measure the current passing through just bulb #3.

14 Breadboard or Circuit Board A Breadboard is an easy way of wiring circuits together. It saves twisting wires together or using lots of leads with alligator clips.

15 Breadboard or Circuit Board All the connections on the “X” row are connected together. All the connections on the “Y” row are connected together.

16 Breadboard or Circuit Board Columns are in two sections: 1A-1E are connected together. Same for the other columns in this section. Columns are in two sections: 1A-1E are connected together. Same for the other columns in this section. Columns 1F-1J are connected together, but NOT to 1A-1E or adjacent columns in this section.

17 Breadboard or Circuit Board This is a picture of the breadboards that I brought along. There are many different manufacturers, but all have the two long strips on either side and the two sections of columns in between.

18 Breadboard Used at Nationals There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold

19 The first two bands give the first two digits of the resistance. The third band is the multiplier that gives the power of ten of the resistance value. The fourth band gives the tolerance of the resistor. The first two bands give the first two digits of the resistance. The third band is the multiplier that gives the power of ten of the resistance value. The fourth band gives the tolerance of the resistor. 1 st & 2 nd Band Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9 1 st & 2 nd Band Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9 3 rd Band Multiplier Black0x10 0 Brown1x10 1 Red2x10 2 Orange3x10 3 Yellow4x10 4 Green5x10 5 Blue6x10 6 Silver-2x10 -2 Gold-1x rd Band Multiplier Black0x10 0 Brown1x10 1 Red2x10 2 Orange3x10 3 Yellow4x10 4 Green5x10 5 Blue6x10 6 Silver-2x10 -2 Gold-1x th Band Tolerance Gold5% Silver10% none20% 4 th Band Tolerance Gold5% Silver10% none20%

20 Practice: Orange Violet Red Gold 1 st & 2 nd Band Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9 1 st & 2 nd Band Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9 3 rd Band Multiplier Black0x10 0 Brown1x10 1 Red2x10 2 Orange3x10 3 Yellow4x10 4 Green5x10 5 Blue6x10 6 Silver-2x10 -2 Gold-1x rd Band Multiplier Black0x10 0 Brown1x10 1 Red2x10 2 Orange3x10 3 Yellow4x10 4 Green5x10 5 Blue6x10 6 Silver-2x10 -2 Gold-1x th Band Tolerance Gold5% Silver10% none20% 4 th Band Tolerance Gold5% Silver10% none20% Orange Violet = 37 Red = x10 2 Gold = 5% TOLERANCE 37 x 10 2 Ω = 3700 Ω 3700 ± 5% 37 x 10 2 Ω = 3700 Ω 3700 ± 5%

21 There are three types of resistors used on this board. The possibilities are: Brown Green Black Gold15 Ω Red Red Black Gold22 Ω Orange Orange Black Gold33 Ω Yellow Violet Black Gold47 Ω Green Blue Black Gold56 Ω Brown Black Brown Gold100 Ω Red Red Brown Gold220 Ω There are three types of resistors used on this board. The possibilities are: Brown Green Black Gold15 Ω Red Red Black Gold22 Ω Orange Orange Black Gold33 Ω Yellow Violet Black Gold47 Ω Green Blue Black Gold56 Ω Brown Black Brown Gold100 Ω Red Red Brown Gold220 Ω

22 Breadboard Used at Nationals One exposed: Brown Green Black Gold There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold 15 Ω

23 Breadboard Used at Nationals Single Resistors. There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold There are three types of resistors used on this board. The possibilities are: Brown Green Black GoldRed Red Black Gold Orange Orange Black GoldYellow Violet Black Gold Green Blue Black GoldBrown Black Brown Gold Red Red Brown Gold Check resistance with meter. 56 Ω 220 Ω 15 Ω

24 Breadboard Used at Nationals Now there are some combinations. Check resistance with meter: 55 to 56 Ω Possible Resistors: 15 Ω, 56 Ω, 220 Ω Four resistors in parallel. Can’t be 15 Ω or 56 Ω 1/R P = 1/ /220 +1/220 +1/220 = 4/220 R P = 55 Ω Aha, each resistor is 220 Ω

25 Breadboard Used at Nationals Now there are some combinations. Check resistance with meter: 11 to 12 Ω Possible Resistors: 15 Ω, 56 Ω, 220 Ω Two resistors in parallel. One is 15 Ω and the other 56 Ω? R P = ( ) -1 = 11.8 Ω No way to tell which is which. R P = ( ) -1 =14.0 Ω too big

26 Breadboard Used at Nationals The nasty one Check resistance with meter: Ω R 8 = ? Ω R 6 = 15 Ω R 7 = ? Ω R 8 = can’t be 15 Ω or 56 Ω so that leaves 220 Ω R 8 = can’t be 15 Ω or 56 Ω so that leaves 220 Ω

27 Breadboard Used at Nationals The nasty one Check resistance with meter: Ω R S = =71 Ω R 8 = 220 Ω R 6 = 15 Ω R 7 = ? Ω R P = ( ) -1 = 54 Ω

28 Concerns: Less expensive meters seem to be less accurate. When students experiment using multimeters, they often wire an ammeter in parallel with a device creating a short and thus a large current which may blow the fuse in the meter. You may not have received replacement fuses and if you have them, they are not easy to replace (you will need a screw driver). If you have many teams competing at the same time, there is a need for many setups. Colleges and Universities have sophisticated equipment. There may be a need to explain how they function. Concerns: Less expensive meters seem to be less accurate. When students experiment using multimeters, they often wire an ammeter in parallel with a device creating a short and thus a large current which may blow the fuse in the meter. You may not have received replacement fuses and if you have them, they are not easy to replace (you will need a screw driver). If you have many teams competing at the same time, there is a need for many setups. Colleges and Universities have sophisticated equipment. There may be a need to explain how they function.


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