©
1996 PASCO scientific
$7.50
012-06247
A
8/96
MOTOR ACCESSORY
Instruction Manual andExperiment Guide for thePASCO scientificModel SE-8657
Includes
Teacher's Notes
and
Typical
Experiment Results
Page 1: ... 1996 PASCO scientific 7 50 012 06247A 8 96 MOTORACCESSORY Instruction Manual and Experiment Guide for the PASCO scientific Model SE 8657 Includes Teacher s Notes and Typical Experiment Results ...
Page 2: ......
Page 3: ...4 2 Operation 3 Assembly Motor Accessory onto the Variable Gap Magnet 4 Assembly Motor Accessory onto the Coils and Cores Set 5 Suggested Uses 6 Experiment 1 Operation of the DC Motor 7 Experiment 2 Operation of AC and DC Generators 13 Experiment 3 Operation of an AC Synchronous Motor 19 Experiment 4 Operation of the Universal Motor 25 Teacher s Guide 29 TechnicalSupport 34 ...
Page 4: ...ment for warranty repair belongs to the customer Equipment must be properly packed to prevent damage and shipped postage or freight prepaid Damage caused by improper pack ing of the equipment for return shipment will not be covered by the warranty Shipping costs for return ing the equipment after repair will be paid by PASCO scientific Equipment Return Should the product have to be returned to PAS...
Page 5: ...mature with split commutator at one end and a dual slip ring commutator at the other brush holder shaft wrench retaining nut maintenance items manual ceramic magnet Additional Equipment Required Variable Gap Magnet EM 8641 or Coils and Cores Set SF 8616 Safety precautions G765 G 73 579 26 C1CC 5 G 8 8 7 311 G 3 2 01213 44 55136 5 8C E5 DH O B 9 8C 35 78D 12 3 1 P 425 7G76 931 2 5B 88 8C 73 72E3 H ...
Page 6: ...x x x x x c o m p uter interf a c e x x x x x x Exp erim e nt 4 Univ ersal M otor no c o m p uter interf a c e x x x c o m p uter interf a c e x x x x x c o m p uter interf a c e x x x x x Lo w V olt a g e D C Po w er Su p ply SE 9720 SE 9712 or simil a r Equipment Options for Experimental Setups with the PASC O SE 8657 Motor Accessory OR OR OR OR OR OR OR 0 1 0 2 3 425 6 5 03 7 8 NOTE Although th...
Page 7: ...ly between your thumb and forefinger and spinning the armature With the Motor Accessory configured as either a DC or universal motor almost any attempt you make at spinning the armature will result in suc cessfully starting the motor only the direction of the spin is important When configured in an AC synchronous mode the motor must be spun at a speed that approxi mately matches the frequency of t...
Page 8: ...ged portion of the shaft Apply increasingly firm pressure equally to each side of the brush holder while rotating the brush holder back and forth If this action loosens the retaining nut tighten it more tightly as described in step 2 Check to be sure the brush assembly is seated as far down on the shaft as it will go Gently lower the armature onto the shaft To make a DC motor the split ring commut...
Page 9: ...y increasingly firm pressure equally to each side of the brush holder while rotating the brush holder back and forth If this action loosens the shaft tighten it as described in step 1 Check to be sure the brush assembly is seated as far down on the shaft as it will go Orient the brush holder perpendicular to the base of the Coils and Cores apparatus Place the two 400 turn coils from the Coils and ...
Page 10: ... 3 72 185 B 2G 8 J1 27C 78D 1213 5B DF 75 G 75 2G 8 4E33 82 93 YE 846 78D 1213 5B DH 6 478 418DE42 D 27 D NB 1372 185 19 2 B3 4 5 18 19 5684 318 5 19 4E33 82 78D 1213 5B D G 2 7 I UZ L C 27 231 1541B 13 0 UZ L C 27 121C72 13 6 1 5 3J 8C 2 5231 1541B 4 99 42 19 78 13D 8736 9 E13 54 82 7 B 72 5 42 D 1213 5B D5H 5 7 3 5E 2F 2 6 D J 1B M 6 4184 B25F 84 ED 8C 2 8D B 8D 84 19 1213 5B D 78D J1 27C F D B ...
Page 11: ...fields The variable gap magnet pro duces a magnetic field that passes through the gap between the pole pieces When current passes through the turns of the armature in the presence of the field forces act to cause a torque that rotates the armature Inertia carries the armature past the position of no torque to the point where the torque would force the armature back in the other direction How ever ...
Page 12: ...e Variable Gap Magnet so there is approximately 1 mm of clearance between the flat pole pieces and the armature when it is rotated by hand Connect the positive terminal of the DC power supply to one end of the brush holder with a red patch cord by plugging the banana terminals into each Connect the negative terminal of the DC power supply to the other end of the brush holder with a black patch cor...
Page 13: ...e that the brush from the lead is touching one of the split rings of the commutator Follow the wire from the split ring to the right coil of the armature and note the direction the wire is wound in the coil Note where the wire enters the coil and where it exits Use the right hand rule to determine the direction the magnetic field will flow when you turn on the power Grasp the coil with your finger...
Page 14: ...m negative to positive for more than a century there was no way to resolve the issue By convention scientists agreed to describe the direction of current as being from positive to negative Not until 1879 did Edwin H Hall show that in metals the current was a negative fluid it remained for J J Thompson R A Millikan and others to demonstrate the existence of electrons which are the charge carriers o...
Page 15: ...s on the two coils become electromagnets with magnetic fields oriented in the same direction which turns the armature into a single electromagnet with its force oriented towards that same direction c True or False In the DC motor you cannot determine the direction of the magnetic field of the armature by determining the direction of the north pole of either of the two coils d What happens to the l...
Page 16: ...gure 2 Predict the direction the armature will rotate when you release it from the position of Figure 2 Will the motor rotate clockwise or counter clockwise If the motor does not start up immediately try turning it by hand in the predicted direction If that fails try turning it in the opposite direction If the motor does not start in either direction turn off the power and ask your teacher for hel...
Page 17: ...tion of motion and the direction of the magnetic field according to the vector equation F qV x B Conductors of course contain charges and moving a conductor sideways across a magnetic field causes a force on the charges that may make the charges flow the length of the conductor if it is part of a circuit The force on the charges can be seen from the equation to be proportional to both the speed an...
Page 18: ...ble Gap Magnet and by detecting the direction of the induced electric current with a galvanometer or multimeter as you move the armature through the magnetic field Setup Be sure you have the flat iron pole pieces placed on the two neodymium magnets of the Variable Gap Magnet The iron pole pieces spread the magnetic field over a wider area Screw the larger threaded portion of the shaft into the thr...
Page 19: ...pole You can verify this by hanging the magnet from a thread and observing that the painted face points toward the North toward the earth s north magnetic pole located in northern Canada Determine the polarity of the variable gap magnet by holding the ceramic magnet near its rectangular pole pieces In the event that both poles of the ceramic magnet attract a pole piece the stronger attraction occu...
Page 20: ...different during the rotation of step 7 compared to step 8 The forces due to Lenz s law in this equipment are much less than other effects and are not readily noticeable Nonetheless the reasoning involving Lenz s law allows you to predict the direction of current Consider the 180 degree rotation you performed above a To oppose the motion during the first 90 degrees of rotation what pole N or S wou...
Page 21: ... repeat the two 90 degree rotations taking about one half second for each Comment on your findings Using the same reasoning as before predict the direction s of the current during the next 180 degree rotation following the one you just made b Test your predictions with the meter and comment c What is different if the armature is rotated in the opposite direction As the armature rotated the current...
Page 22: ...What is the effect of greater rotational speeds b This result may be explained in terms of the ideas discussed above Try to explain the effect of greater speeds If you have a PASCO computer interface and Voltage Sensor try this a predict how a voltage vs time graph would look if you put the dual slip rings down and spun the armature rapidly and let it slow to a stop b What if the split rings were ...
Page 23: ...that passes through the gap between the pole pieces When current passes through the turns of the armature in the presence of the field forces act to cause a torque that rotates the armature Inertia carries the armature past the position of no torque to the point where the torque would force the armature back in the other direction Instead if the rotational speed of the armature matches the frequen...
Page 24: ...earance between the flat pole pieces and the armature when it is rotated by hand Procedure Part A Remove the armature from the shaft by grasping it between your thumb and forefinger and rotating it back and forth while lifting gently If necessary insert a pencil between the brushes to gently separate them so they don t prevent removal of the armature Examine the armature closely and imagine curren...
Page 25: ...rmature Explain why c True or False In this AC motor we can determine the direction of the magnetic field of the armature at any instant by determining the direction of the north pole of either of the two coils Imagine that the AC current is in the negative half of the wave form This means that conventional current comes out of the terminal marked negative of the power supply and enters the termin...
Page 26: ...The painted face of the magnet is its North Pole north seeking pole You can verify this by hanging the magnet from a thread and observing that the painted face points toward the North toward the earth s north magnetic pole located in northern Canada If both poles of the ceramic magnet attract the armature the pole with the stronger attraction will be the opposite pole Verify that the result of the...
Page 27: ...photogate as follows Cut a 3 cm square from corrugated cardboard and punch a hole that is 1 cm in diam eter in the center a 4 cork boring tool works well If the square slips you may need to secure it with tape Slip the square part way down the split ring commutator so you can grip the plastic bushing to spin the armature Position the photogate so the corners of the square interrupt the photogate s...
Page 28: ...eded Does the rotational speed of the armature change when you change the current frequency 11 If the room is lit with fluorescent lights you can also see the effect changing the current frequency on the motor s speed Fluorescent lamps flash twice during each cycle of the AC power that supplies them When the motor operates at a submultiple of this rate multiple images will appear to be stationary ...
Page 29: ...om the fact that it will operate on either DC or AC current With alternating current the changes in direction of the current cause reversals in both the poles of the U shaped core and the armature so attraction or repulsion between poles is the same as with direct current In terms of the magnetic fields with direct current the magnetic field of the armature reverses every half turn and the magneti...
Page 30: ... or repairs Procedure Connect the motor the power source as shown in Figure 2 All connections may be made by inserting banana plugs into the openings in the ends of the plastic brush holder and the external coil forms Do not turn on the power source yet Rotate the armature and observe how the segments of the split ring commutator contact different brushes as the armature turns Remove the armature ...
Page 31: ... coil Grasp the coil with your fingers wrapped around the coil in the direction of the current Your thumb will point in the direction of the field that is toward the north pole of the coil Label the ends of the coil N and S in Figure 2 Figure 2 Experimental Setup Gently replace the armature onto the shaft The split ring commutator should be down Carefully rotate the armature back and forth to sepa...
Page 32: ... agree with your labeling of the figure Determine the polarity of the U shaped core in the same way Label its poles N and S in Figure 2 Predict the direction the armature will rotate when you release it from the position shown in Figure 2 If the motor does not start up immediately try turning it by hand in the opposite direction Turn off the power and reverse the leads to the brushes Before turnin...
Page 33: ...er to create a greater effect No a Yes b True c False d The location of the armature s north pole alternates between ends of the armature as the lead touches the alternate sides of the split ring commutator e The current is alternating in the coils because one side of the split ring commutator sends the current in one direction in the wire while the other side sends it in the opposite direc tion i...
Page 34: ...f the DC current Experiment 2 Questions Part A AC Generator a It increased b An emf electromotive force or voltage will be induced in the coil a It decreased b An emf will be induced c The emf will be opposite in sign or direction in the two steps because the change in flux within the turns is opposite in the two cases In one case it is increasing in the other case decreasing a It should be a nort...
Page 35: ...ausing electron movement 2 Faraday s law states that the emf induced is proportional to the rate at which the flux in the loops of the coils is changing At higher rotational speeds the rate of change to the flux is greater and thus so is the emf a The voltage vs time graph would be a sine wave whose amplitude and wave length or period is decreasing to zero b It would be the same as a except all po...
Page 36: ...y reverses is the same but the force of the induced magnetic flux of the armature decreases with the decreased voltage a The rate of vibration is lessened and the strength of the pulsation is increased b The halving of the cycle rate of the AC results in halving the rate of reversal of polarity in the armature while the increase in voltage results in the increase in strength of the pulsations The ...
Page 37: ... You may want to challenge the students to predict and test what happen if DC is applied to the armature while AC is applied to the coils Counter clockwise as viewed from above The motor should turn clockwise The motor s speed will decrease The motor should operate at a high rate of speed but not in synchronism with the alternat ing current source Reversing the direction of current flow from the p...
Page 38: ...Motor Accessory 012 06247A 34 Notes ...
Page 39: ...ould be helpful to prepare the following infor mation If your problem is computer software related note Title and revision date of software Type of computer make model speed Type of external cables peripherals If your problem is with the PASCO apparatus note Title and model number usually listed on the label Approximate age of apparatus A detailed description of the problem sequence of events In c...
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