# What is Dynamo: Definition and 49 Discussions

A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using rectifiers (such as vacuum tubes or more recently via solid state technology) is effective and usually economical.

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1. ### B The historical war of currents in Mains Power Distribution: AC vs DC

So, if I get it right, the basic argument goes like this: AC was preferred to DC because its voltage can be stepped up by a transformer. This limits losses while the current is transported from the production plant to the final user. The voltage is subsequently stepped down when delivered to the...
2. ### Induction heater using Bicycle Dynamo Generator @ 24 V 60HZ Supply

I was wondering about the possibility of Induction heater powered by Bicycle Dynamo (alternator/generator) without using any other circuit element. Which means connecting 24 V 50 to 60 HZ AC to Coil with turns around 100 in pancake shape (10 inch diameter ) and Stainless steel plate of 3 mm...
3. ### I Can a Core-less Dynamo Really Achieve Double Efficiency?

It seems that a core-less dynamo would have a maximum efficiency of 2. The argument is as follows: JxB emf= E.J emf JxB does no work E.J does work Thus output is twice the mechanical energy spent Inward Poynting vector?
4. ### I Can I Calculate the Current and Tension Produced by a Dynamo?

Hi, I was trying to read about the current produced by a dynamo in my physics books but I can't find any reference. I have a rotor rotating at a certain speed, air flow and with a certain inertia, but how can i find the power produced and related current and tension?
5. ### I Is the Sun's Magnetic Field Driven by a Double Dynamo?

Is the sun's magnetic field generated by a double dynamo? https://www.ras.org.uk/news-and-press/2680-irregular-heartbeat-of-the-sun-driven-by-double-dynamo Sorry if it was discussed yet but I couldn't find it.
6. ### A question about the Dynamo Theory

I'm studying Dynamo Theory, and have just a few questions. Today's theory says that currents in the molten outer core of the Earth give rise to magnetic fields. Now it would seem that the theory does not mean "molten iron currents", since together that is an electrically neutral substance, but...
7. ### How can the neutral outer core generate a magnetic field?

Even if the outer core is convecting and conductive it is still charge neutral, so how can a Magnetic field be generated? Maxwells Equation say there needs to be net charge moving for a Magnetic field to be generated.
8. ### The rate of change in the magnetic field linkage in a coil

Hi, I would appreciate it if someone explains the difference between these two phases regarding a coil rotates in a uniform magnetic field. 1. The rate with which the coil intercepts the lines of magnetic field in the dynamo is maximum when the plane of the coil is parallel to the lines of the...
9. ### The magnetic flux and the induce emf in the dynamo.

Homework Statement Multiple-choice question: Homework EquationsThe Attempt at a Solution I know that the induced emf is maximum when the coil is parallel to the direction of the magnetic flux, so I should choose either B or C, and I have read the the rate by which the coil cut the magnetic...
10. ### Dynamo design with regenerative back mmf

In the above presented dynamo design, three snapshots taken during three instances during the rotor running. In fig 1 the approaching magnet builds an induced voltage across the coil, however the circuit is still open, hence no current flows. In fig 2 when the rotor reaches TDC (top...
11. ### I Question about a magnetic dynamo on tidally locked moons

All, Non-scientist amateur looking for an answer. I understand that planetary rotation aid is vital to maintain a magnetic dynamo. Venus' slow reverse rotation is often used as an explanation for its odd low magnetic field. Assume there is a moon or a double planet that is tidally locked...
12. ### Can a Motor be Converted to a Dynamo and How to Do It?

Hey, I understand that essentially a dynamo is the inverse of a motor however I was wondering if I could have a little more detail on the subject, how exactly can you convert a motor to a dynamo? Is it as simple as turning the motor and wiring it up to an output to create the current or do you...
13. ### What governs how hard it is to turn a dynamo?

Say I wanted to attach a dynamo up to some pedals or something - what factors would affect how hard the shaft would be to turn? Is it governed by the physical configuration of the dynamo (windings, etc)? Or is it the (electrical) load attached that matters - and how does that work? If I wanted...
14. ### Does a Torus dynamo actually work?

Hi all, in short does a Torus shaped generator actually generate any useful power? If so, is there any formula/calculator that can predict its output in watts? I've seen some claims online but I'm skeptical. They are basically like a shake torch with a solenoid mechanism in a torus shaped...
15. ### Optimizing Miniature Dynamo Systems for Efficient Energy Generation

So..What would be the most efficient miniature dynamo system? So my question to you, on the small scale, what would be the most efficient dynamo system? Small scale meaning a handheld size device. I know energy can be generated using Faraday's law, when you move a magnet near a coil it...
16. ### Connections between motor and dynamo

Hi everyone, I am currently trying to find out if it is possible to make such connection. Main supply power up Motor B, Motor B uses its mechanical load to run Dynamo B, Dynamo B generate electricity to power up Motor A. Is it possible for such connection? I have made such setup and I...
17. ### Generator Project: Designing a Self-Powered System with Batteries & PLC

I'm a graduating student of Electrical Engineering Technology (3 years) and so one of our graduating subject is thesis. We decided to make a generator that can supply the house and supply itself by giving some of the power to back to the motor which rotates it. We also included batteries and...
18. ### Uncovering the Mystery of Non-Linear Torque in Muscle-Powered Energy Conversion

Hi, i didnt know where to put this question cos its kind of multitopic, here is why... I am working on a better way to take mechanical energy from muscles, i made a teste bench for pedalling in very different ways, including traditional(circular) pedalling, the thing is. I am measuring the power...
19. ### Faraday's Dynamo & kinetic energy

Homework Statement (The picture is not from my textbook) A Faraday Dynamo is used as a brake. The brushes are connected with an external resistance R_\Omega. The circular disk has mass m, and angular velocity \omega_0 when t = 0. a) How long does it take until the kinetic energy of the disk...
20. ### How Do You Calculate Induced EMF in a Dynamo?

I want to know how I can calculate the induced emf in the dynamo, I don't know how I can translate the change of the rotating coil's area into an algebraic equation. Thanks in advance.
21. ### Dynamo vs Motor: Exploring the Differences and Efficiency for Power Creation

I hope this post doesn't get deleted again. This forum moderator has something stuck up his you know what. Keeps deleting posts that I make that he considers speculative. So I guess every thing we know about our universe is all we'll EVER know. Because if you can't speculate you're stuck...
22. ### How does a dynamo produce electricity?

Hello guys, I have a few questions to ask and I really need an answer for them all. Firstly, I know that the Dynamo or the Generator produces electricity to the vehicle engines and houses, etc... But I seriously want to know how Dynamos produce electricity exactly. I didn't understood exactly...
23. ### What Dynamo to Use? Get Help to Charge Battery 3.5V 1000mA

Hello I am working on a project to charge a small battery say of 3.5 Volts and 1000 Milli Amp through cranking/wind up but I am not able to figure out what dynamo is required and how much time I would have to crank in order to draw the required power(3.5 Watts) in order to charge the battery...
24. ### A Reverse Dynamo - Opposite to the Shake Flashlight

I would like to know if it's possible to build a dynamo that instead of having an electrical current driven through a coil by movement of a magnet to generate electricity could be driven by ac to move the magnet or coil in a vertical motion instead. If so, (which logically it sounds possible to...
25. ### Electricity generation - simple bike dynamo - can anyone explain this design?

http://img404.imageshack.us/img404/9523/dynamos.jpg I understand that when the rotating magnet spins, current should be induced in the coils which powers the lights. So what is the point of the soft iron core? The rotating magnet should magnetise it because it is near it, and it should...
26. ### Creating Linear Dynamo - Instructions for Les

Hi, I am currently working on a project for university, The initial idea I had was to use piezoelectric materials but it is too expensive, so I am going to try and change the way the system works, but in order to do it, I need to create a linear dynamo, Could anyone tell me if it is...
27. ### Contactless dynamo for my road bike - help with the magnetics please

Hi all, Would appreciate some help with the magnetics in a contactless dynamo I'm trying to build for my road bike to power some LED lights. I've got 8 rare-earth magnets mounted on the bike wheel, near the hub. They're flat, round magnets, around 2cm dia., mounted all the way around the...
28. ### Connecting a dynamo to bicycle to get electricity

How do I do any calculation when I want to know what kind of a dynamo I need to connect to my fitness bike to produce electricity? And then, what kind of batteries?
29. ### So how exactly does Dynamo do it?

Dynamo the street magician has a show on Watch TV. Some of the things he has done is hown to walk on water, go through panes of glass, change bank note numbers and the lettering on a cinema sign by blowing on it from the other side of the street...
30. ### Can a Mock Demonstration of Earth's Core Dynamo Effect Be Created?

Hi, Does anyone know if anyone else has made a mock demonstration of the dynamo effect of the Earth's core? I've heard that the core is supposed to be made of a liquid metal sphere with a solid metal core. When they spin, they make the Earth's magnetic field. The question is, if the...
31. ### Dynamo to charge battery using electromagnet.

Homework Statement A team on The Apprentice have to come up with a new electrical device. They propose a hand cranked dynamo to charge a battery which initially uses the residual charge in the battery to power the electromagnet, instead of a permanent magnet (the idea being that this...
32. ### Building a Dynamo: Components & Voltage Production

Basically would just like a summary of the components that are required in order to create a small dynamo. And also, any ideas how much voltage can be produced from one? Any help would be greatly appreciated.
33. ### Creating a Dynamo System: What Components Are Needed?

Just need a bit of clarification, I am attempting to make a dynamo system but not totally sure where to start. What components would be required? It needs to be pretty small, similar size to that used in a wind-up torch, and it will be required to produce heat rather than light. Any help...
34. ### Dynamo Drag: Does Adding a Coil Increase Resistance?

I was wondering; Imagine two situations: 1) I rotate an axle with a strong magnet attached within a conductive coil (a dynamo). 2) I rotate an axle with a strong magnet attached without a conductive coil. Does the presence of a coil (and therefore the generation of current in the coil)...
35. ### Charging from Dynamo: Help for M Rashid

I want to charge from dynamo (bycycle dynamo 12 volt) with emergency light 6 voft 4.5 ah. (builtin charger). Please help me. Thanks. M Rashid
36. ### Can a self-exciting dynamo generate electricity without any mechanical input?

self exciting dynamo question I was reading about dynamo's and there was one that the power it made was used to run the electromagnet that made the magnetic field that the induction coil spun in. This got me thinking if a generator can make enough electricity to power an electromagnet that is...
37. ### Faraday's Disk Dynamo: why is there an emf?

Consider a rotating disk on a uniform magnetic field. Faraday's law states that \epsilon = - \frac{d\phi}{dt} In this situation, \vec B is constant and the area of the disk is constant. Hence, the magnetic flux is constant and there should be no emf. What am I missing?
38. ### There is a magnetic friction force in a dynamo?

There is a "magnetic friction force" in a dynamo? In a rotating dynamo, where the magnet rotates surrounded by a coil, there is something like a "magnetic friction force"? The magnetic field causes an effect similar to mechanical friction, that can slow down the revolving magnet?
39. ### Can a Simple Relay Prevent Damage from High Voltage in a Hub Dynamo?

Hi, I am wondering if you can help: I have a hub dynamo that I would like to use to charge my mobile for a cycle ride across europe. The DC hub dynamo produces anything up to 40volts at full pelt! So I want to use a car charger to charge my mobile phone (and one for a camera), which I...
40. ### Calculate Dynamo Max Power Output

Hi, I have a small DC dynamo (with no spec sheet) which i digitally sample to find it's voltage at any given time. I want to display theoretical max power output, how can I calculate this? Can I use P=V^2/R where V is measured. How do I calculate R? I read a wikipedia article which says to...
41. ### Dynamometer Principle & Operation | Load Testing Accuracy

Dear all The eddy current dynamometers are used to load testing of motors and gearboxes.Can anybody explain the principle and operation of dynamometers and load testing accuracy.? Thanking u Prakash
42. ### Need help with Dynamo rule applied to coil and magnet:

Hi, (I posted this on TSR as well, but they're being a bit slow...) Take the following setup: If you move the bar magnet left and right (a few cm) inside the coils, so that the ends do not leave the coil, will it induce a current/emf? I presume it does so, as I have been taught. But I don't...
43. ### Electromagnetic induction; bike dynamo

Hi, I am trying to learn more about electromagnetic induction because I want to build a generator for a wind turbine. I am a bit confused about something, hopefully someone out there can help me! I recently opened a bike dynamo. It contains a permanent magnet that can rotate, and the...
44. ### Dynamo, Generator, Alternator?

Hey, bit of an odd projection question here, Im working on generating a current(enough to power a few leds) in a juggling club. I was originally thinking of a "shake" generator like this <a href="http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p020.shtml" >This</a> With...
45. ### How much energy do i produce with my dynamo while cycling ?

I was on an exercise bike in the gym the other day and on the screen it said I was generating 138 watts, and as you can imagine that's a pretty big value,lol. I wasn't cycling that fast either. My question is, is this value possible ? sorry if this is a bland question but I know a wind...
46. ### Bicycle Dynamo Light Circuit: Understanding the Wiring and Functionality

Hello! I have one question. How the circuit of the dynamo light of bicycle is closed? Isn't the coil got two wires, one from the start, and one from the end. Thank you. Regards. Here is one picture: http://www.windpower.org/kres/dynbde04.gif
47. ### 12v DYNAMO driving 5v front & 10v rear LED lighting + DIAGRAM

Hi, I'm wondering how to drive front and rear lights off one dynamo. See diagram for current setup. Lights are hooked up to dynamo in parallel. The LM7805 and LM317 are voltage regulators which drop the voltage from 12v to 5v and 10v respectively. Currently only the headlight works, the...
48. ### Will a superconducting dynamo in space produce free energy?

I have read in several places that superconducting materials are the closest phenomenon to perpetual motion known to science (constant flowing electrons within a circuit without resistance). The problem is that the energy required to cool the inducting material to its superconducting temperature...
49. ### Paleo reversals and the dynamo effect

Hi, I am exploring a theory and would like your initial reaction to it. The latest research unfortunately I do not have access to however I think there may be an easier way to understand the magnetism created by the Earth dynamo by realising that it is simply the sum of all the dynamos...