# toroid Definition and Topics - 9 Discussions

In mathematics, a toroid is a surface of revolution with a hole in the middle, like a doughnut, forming a solid body. The axis of revolution passes through the hole and so does not intersect the surface. For example, when a rectangle is rotated around an axis parallel to one of its edges, then a hollow rectangle-section ring is produced. If the revolved figure is a circle, then the object is called a torus.
The term toroid is also used to describe a toroidal polyhedron. In this context a toroid need not be circular and may have any number of holes. A g-holed toroid can be seen as approximating the surface of a torus having a topological genus, g, of 1 or greater. The Euler characteristic χ of a g holed toroid is 2(1-g).

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1. ### Engineering What is the magnetic field of a half toroid?

Hello, I would like to know what is the magnetic field of a half toroid. Would we use Ampere's law? So, considering that the integral is equal to BA, we would have BA = μo * i, then B = (μo * i) / r. But, using Biot-Savart's law, by symmetry, it seems that the vector sum of all the...
2. ### Electric field due to a Poloidal Magnetic Field in Toroidal Magnetic Confinement of a Plasma

Please be kind to help. How is an electric field formed due to toroidal magnetic field? How does the introduction of a poloidal magnetic field confine the plasma? Please answer in the context of Nuclear Fusion Reactor (tokamak).
3. ### Why does the current have no ##\phi## component in a toroidal coil?

These are images from the book Introduction to Electrodynamics by David J. Griffiths . . . My problem is that I'm unable to understand how the current has zero ##\phi## component (I have underlined it in the first image)? I do understand cylindrical coordinates, I know...
4. ### Self-inductance of a toroid with a rectangular cross section

I have found answers on how to calculate the self-inductance of toroid of rectangular cross section, however my question says that "The winding are seen as a thin homogeneous currentlayer around the core" (excuse the translation). What does that mean for N? Does it mean N=1?
5. ### Nuclear Fusion: Electron Thermal Transport Terminology

I am an undergrad physics major in my final semester currently taking Intro to Thermodynamics. As a final project, each student must choose a topic related to thermodynamics that is more advanced than what is covered in the curriculum and write a paper and present our findings to the class on...
6. ### I Movement of a iron ring inside a toroidal solenoid

What happens when you apply power to a toroidal solenoid with a iron ring inside? Does the ring move? Does the speed of movement depend on the amount of power? Sorry if this is too easy, I have no education in physic.
7. ### Electromagnet magnetic field strength

Homework Statement Homework Equations ##\oint_{C} Bd\ell = \mu I_{enc}, B_{normal}## continuous across boundary, ##H_{parallel}## continuous across boundary The Attempt at a Solution $$\oint_{C} Bd\ell = \mu I_{enc} \rightarrow B = \frac{\mu NI}{2\pi r}$$ Any help much appreciated. How...
8. ### Total internal confinement of magnetic field

Hi, I heard it was possible if you symmetrically wind a toroid that you can get near total internal confinement of the magnetic field in the axial plane inside the toroid. How is this possible? I imagine a section of a closed loop of wire on the face of the toroid core, yet I still imagine those...
9. ### Calculating the B field in a small gap in a toroid

Homework Statement Take a steel core (K_m = 2500) electromagnet, bend it into a loop with a small air gap, and determine the B field in the gap. The cross-sectional area of the toroid is 4cm^2, and the air gap is 2.5mm. The current through the coil's 120 turns is 15 amps. The radius of the...