What is Motors: Definition and 333 Discussions

An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion.

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  1. Low-Q

    The problem explaining how homopolar motors work

    Since I discovered the homopolar motor, it has fascinated me a lot. Not because it has any practical use, but it works in spite of a non gradient magnetic field. Normally, an electric motor works because the rotor is allways "chasing" a sticky magnetic spot. The magnetic gradient between weak...
  2. A

    How exactly do motors and generators work by using magnetic fields?

    So I know if you move a charge in a magnetic field it induces voltage and hence a flow of charge is created which is current. ( Please correct me if I'm wrong). But that's pretty basic right. However, I'm having trouble understanding the use of split rings in the functioning of a motor. I would...
  3. A

    Automotive Two small fan motors one rotates faster when other is jammed

    i made a small thing for my nephew, i connected two small fan motors with one switch and one battery but everytime one of the motors jams or he grabs the fan the other fan rotates faster. why is that? also tried to increase number of batteries but same thing
  4. Paul Colby

    How do the motors for read-write heads in HDs work?

    I've dissected several hard disk drives to scavenge the "linear" motors which move the read-write heads across the disk platens. At first glance these look simple enough. There is a pair of high energy permanent magnets in a yoke which provide a circular sector shaped high magnetic field in a...
  5. T

    Understanding Linear Motors: Right Hand Rule & Current Flow

    Hi there, I attached an image of a basic linear motor. I'm a little confused if I use the right hand rule or left hand rule. I did it both ways and I think the left hand rule is the only rule that allows for a force being applied to the right. I assume the current is going down rather than...
  6. C

    Optimum Wheel Radius for a Terrestrial Robot

    Hello everyone! This is my first post here so please excuse me if I don't have the format right yet. Background: I'm a Mechanical Engineering student working on a robotics team and I'm tasked with designing the wheels. The robot is currently using 5 in radius wheels with old motors. The...
  7. S

    Calculate Motor HP at Reduced Frequency & Speed

    How does one calculate the amount of HP a motor makes when it is not running at a full 60Hz? The reason for my asking is a customer wants to use a 1/4HP motor and a gearbox to vary the speed of a conveyor. At a full 60Hz we are figuring 1750rpm for the motor, and through the 7:1 gearbox the...
  8. T

    Electric motors vs internal combustion engines

    On average, which has higher power to weight ratio between the two? So on average, if both weighed the same, which one is going to have more power?
  9. T

    Can electric motors possibly apply continuous upward force?

    Is it possible for an electric motor to exist (based on our current understanding) which is capable of applying continuous upward force upon an object, enabling that object to fly or lift above the air?
  10. yrjosmiel

    What are the advantages and disadvantages of n-pole motors?

    From what I've understand now, it is like in a brushed DC motor, the more poles you have, the less RPM but higher torque. Can anyone confirm?
  11. R

    Question about power capacity of electrical motors

    I read that the Tesla electric motor is able to achieve its remarkable power to weight ratio of 8.5 kW/kg, about 10 times better than a typical gasoline engine, because it tightly winds its copper wires in its coils therefore being able to carry more current in the same space. If so, then we...
  12. N

    How can I achieve higher speeds when running stepper motors?

    Hello all. Thanks for taking up your time to read my post. I have ordered http://uk.stepperonline.com/download/pdf/11HS20-0674S-PG14.pdf stepper motors. I asked the seller how many revolutions the motor can achieve in a minute and they answered 43. I calculated (13 + 212/289) * 200 * 43 / 60 to...
  13. O

    Switched Reluctance Motors: Nonlinear Loads?

    Homework Statement Would a switched reluctance motor be described as a non linear load? Since it is switched on and off rapidly to turn the rotor, does that make it non linear?
  14. Jack of some trades

    Capacitors on motors: why big C for starting, small for running?

    Long story short, on single-phase capacitor motors, large values of capacitance are used for starting and much smaller values are used for running. Yet it would seem that the amount of electrical phase shift needed is dictated and fixed by the physical relationship between the main and auxiliary...
  15. quickquestion

    Best place to buy the best cheap motors

    Basically, I am looking to buy some cheap motors. Basically, I am trying to build a small 1 person car that can drive on the sidewalk. Trying to find out the best and cheapest small motors. Preferably with a throttle. These motors would only need to move 250 lbs at 20 mph or 30 mph. I want...
  16. B

    How do changing magnetic fields affect the speed of motors?

    Motors are supposed to rotate inside because of changing magnetic field.. but when looking at high speed fan.. I'm thinking how can the changing magnetic field responds so quickly... is the rotation or changing magnetic/electric field the same speed as the fan?
  17. jlmccart03

    Find alternators magnetic field?

    Homework Statement You're an electrical engineer designing an alternator (the generator that charges a car's battery). Mechanical engineers specify a 10-cm-diameter rotating coil, and you determine that you can fit 250 turns in this coil. To charge a 12-Vbattery, you need a peak output of 16 V...
  18. B

    How to obtain the parameters of DC motors?

    Hello, I appreciate if somebody could help me to resolve this. I bought a geared DC motor from a store. I would like to obtain the following information: Resistance, Inductance, Back EMF constant, torque constant, and the voltage caused by Back EMF when the motor is supplied by a voltage input...
  19. Asher Kabir

    How can I teach how a motor works to students effectively?

    I'm a physics teacher and I've found it hard to explain motor's working to a couple of students.
  20. N

    How large of a flywheel can my motor spin?

    Hi All, I'm hoping you all can help me with what I think should be some relatively simple calculations. I'm looking to determine how large (diameter / weight) of a flywheel a particular AC motor can spin from a stop to full RPM given the torque / HP of the motor. For instance, if I have a 1/3...
  21. P

    Exploring Tesla's Autos & Induction Motors

    As a EE student, I studied Induction motors: three and single phase. I saw somewhere that Tesla's autos are using induction motors feeded by batteries. But I've never heard about DC induction motors.. I also heard that Tesla autos have torque constant for every speed, but that's also not how...
  22. D

    DC motors in parallel causing voltage drop

    Hey PF, first time here, I have a problem I can't seem to solve! Any help is appreciated. I am using some DC motors with peristaltic pump heads to pump water (picture). I was having issues so I've broken my circuit down to the bare basics: 1) 12V regulated power supply 2) 12V motor 3)...
  23. William123

    Will these two brushed DC motors reach the same RPM

    Hi I'm working on a project in school (or at home) about brushed DC motors. I have recently built a prototype myself but instead of using permanent magnets around the armature I'm using an electromagnet from another motor that died. I intend to build another motor using the same armature but...
  24. S

    Motors in series: how do you stop one motor from spinning?

    Hi All, I've been reading up on hybrid vehicles and how the Honda Insight has an electric motor attached directly to the gas engine driveshaft. Their combined output causes the wheels to spin. My question is in regards to when the electric motor is off but the gas engine is on. Why doesn't the...
  25. kenok1216

    Engineering How to find short pitch and pole pairs of motors

    Homework Statement Homework Equations p=nsf δ=mϒ Kd=[sin(δ/2)]/msin(γ/2) Kp=cosε/2 e.m.f=4.44TφfKdKp The Attempt at a Solution i do not know why pole pair =2 and it is short 2 pitch. how can i find pole pair and short pitch from its original developed diagram? i know that Phase spread=60(we...
  26. marcophys

    Rising voltage leak to 100v AC - 220v 50Hz 35uF 1.5KW motors

    I noticed that I could get a minor belt off my 3 x 1.5KW compressor. I attached my meter to a mains supply 'socket earth', and to 'the chassis'. I watched the AC voltage gradually rise... perhaps increasing in speed slightly as the potential difference increased between the chassis and earth...
  27. Gurfin321

    Electric Longboard Gear Ratio

    I would like to know what gear ratio i would need for my electric longboard. The goal is to run the longboard at 30 - 40 km/h at max power. Me and the longboards weight is approximately 65 kg. The brushless motor i am running has an rpm of approximately 18000 rpm (as it is an airplane engine)...
  28. E

    What's about no air-gap in motors?

    Hi, I saw few threads here about air-gap in motors, and I wonder what if we ignore mechanical issues and make an "iron-gap" in the motor. for example: in linear motor(e.g. this cute one: https://www.physicsforums.com/threads/linear-motor-equations.794499/) if we make the tube between the stator...
  29. Bryan Deily

    Running Two Brushed 12V DC Motors

    I am trying to figure out the best way to hook up two 12v DC peristaltic pumps to run as close to the same speed as possible. The manufacturing tests had the pumps running within 10ml per minute which is acceptable; when I hook the pumps up in series they are not even close. When hooked up in...
  30. Planobilly

    Using 400V 50Hz 3 phase motors with 240V single phase 60Hz

    Hi, We have a machine from Europe with three 400V 50Hz 3 phase motors. Assume we only have 240V single phase available. There may be 480V single phase available. I don't currently know how many poles the motors have. Assume they are not made for both 50Hz and 60Hz as some are. Power consumption...
  31. James Birt

    I have a 2-part question about electromagnetism and motors

    So, I'm working with a DC shunt wound motor and I want to calculate the actual voltage production on paper mathematically before building. I have been studying the biot-savart law and understand it to a fair degree. One of my questions is after you get your measurements in Teslas from said law...
  32. shina

    Electricity and the operation of induction motors

    How electricity passing through a conductor produces magnetic field around it. How an induction motor works. The energy or electricity which passes trough green earthing wire is transmitted into the ground. Why this energy is not conserved and can be used in future. All these three things are...
  33. M

    Need help with wiring motors in series and in parallel

    Hello, I'm working on my kids ride on cars. He has two of them. On the first it was 6V and came with one motor on one wheel. I updated it to 2 motors, one on each wheel and 12Volts. I put in a DPDT switch so he could select high and low. On high the motors are run in parallel and on low they...
  34. G

    Induction motors and power factor

    Hi all, I have a 1 HP capacitor start motor (old, c.1950) that runs an air compressor in my little workshop. When it's running, the lights in the shop and the whole house dim and brighten rhythmically, at about 5 Hz. This, of course, is related to the compression cycles of the compressor, but...
  35. K

    Automotive How do I calculate required torque for two dc motors?

    Hi, I am doing a design project but I'm kinda stuck with choosing motors because i am not sure of the required torque. My project is a handicapped golf vehicle powered by 2 motors, so it would need to be able of climbing steep gradients. I currently have an equation but I am not entirely sure if...
  36. R

    Can multiple motors drive single axle (water pump here)

    I have a dilemma with the design of a device I want to build which is acquiring the correct size motor (shape & power) in my price range (even finding one within specs). I have found that the motors from cordless drills are ideal for this application (due to size, price and availability) so...
  37. A

    Electric Bike Motors: Size, Wire Gauge & More

    I have been reading up on electric bike motors, there are a few things regarding size and wire gauge that have me confused. I have seen disassembly videos of around 300 watt electric bike motors with planetary gears, and I can't see how anyone can push through 300 watts through the wires without...
  38. srinaath

    Why single phase induction motors are used for fractional HP applications

    why single phase induction motor is commonly used for low HP rather than integral HP like 1,2,3HP... i understand that single phase gives low power...but say you have designed such that your motor delivers 10HP for rated voltage and current...why such single phase machines are not common?can...
  39. D

    Automotive Selecting electric motors once power requirements are calculated

    So for a school project I got to design an electric car that can meet minimum range and top speed requirements for how heavy it is. I have calculated the amount of power needed(kW) for its heaviest load situation to reach the min speed and range, along with the necessary energy(kWh) required...
  40. Metals

    Propellers on an RC Quadcopter?

    Hey forum, So I plan on creating a remote controlled quadcopter and I have a query regarding its propellers' sizes. I read that small propellers require motors with a high KV (RPM per volt), and large propellers need motors with a lower KV. There seems to be a way of determining how to match...
  41. dubya_80

    Variable speed control of multiple dc motors

    I'm building a hybrid car for my kids. I'm up to speed control and hitting a few hurdles. The set up is 4 x 12VDC motors, one to each wheel through a reduction gearbox. I've wired them to a single bus, and have used 4 standard relays to deliver forward/reverse. I have tried varying the speed...
  42. P

    I dont understand homopolar motors

    I understand the diagram above where the blue stuff might be mercury like in Faraday's mercury motor. I don't understand why the liquid moves but... it is a conductor so why doesn't the current (moving electrons) feel the force and leave the liquid stationary? Similarly in this motor its the...
  43. S

    Cheapest/best power supply for 7 different types of motors

    Hello community, I am building a device for which I will be using five Stepper motors (each 5v, 3a) and one brushed DC motor whose speed has to be varied and operates between 12V and 48V (350Watts). Also I have a heater which runs at 12V, 40Watts. My question is: How will I best power these...
  44. cnh1995

    Cascade connection of induction motors

    In cumulative cascade connection of two induction motors, why does the net speed reduce? Also, how are the torques of the two motors in the same direction?
  45. carolinern

    Engineering Just starting out on DC motors and hit a snag

    Hi Guys I'm hoping someone can help me out with a problem?? I have just started learning about DC motors and I have hit a wall on how to solve the following problem- Q.The output of a series d.c. motor when connected to a 230V supply and running at 1320rev/min is 3.8kW. The supply current for...
  46. G

    Do motors have some voltage drop across them

    Homework Statement Homework Equations Hello, i have been thinking, what couses a dc motor to have let's say 6volts drop across him. I was thinking that since it is just a coil it should have a verry little voltage drop, but afted testing on breadboard i figured out that it have near 6 volts...
  47. AngelaG

    Deciding Between Baldor & Leeson Motors for Smaller Size

    hi people, Im getting a motor but can't decide between baldor or leeson so Id figure I might try to ask here: Single HP 1725 or 1800 RPM Three Phase TEFC preferred 56C frame size Is just one of the brand names preferred with a smaller motor? III be shipping this to my place back home, when I...
  48. T

    Rear wheel drive with separate motors

    I have built a rear wheel electric with two motors one for each rear wheel. The motors have separate controllers and both are controlled by a single throttle. This throttle sets a torque for the motors . In a straight line the torque is the same for each but when cornering the torque setting is...
  49. T

    How can I safely salvage and understand basic motors at home?

    This is my first post, so please excuse any mistakes I might make. Sorry in advance. First and foremost, if anyone thinks I am being unsafe in any way, please let me know. I like to do things hands-on. I learn best that way, but I want to be safe. I am a budding electrical engineering student...
  50. B

    Poles of AC Induction Motors

    Hello, I want to know determining the number of poles by inspecting coils inside the motor. Generally, there are formulas allowing us to plug a frequency, an rpm, and give off the number of poles, or we can just simply look at its nameplate. My reason for needing the inspecting is that my...
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