# Is the B Field Constant Inside a Toroid?

• cragar
In summary, the conversation discusses the constancy of the magnetic field inside a toroid. While amperes law can be used to find the field, there is some confusion as to whether it is constant or varies with the radius. The individual also mentions that the field is stronger on the inside edge and weaker on the outer edge.

#### cragar

Is the B field constant inside a toroid?
Like we would just use amperes law to find.
B(2*pi*r)=(mu_0)NI
But after talking to this kid he said it changes inside. But i thought it was constant.

Last edited:
cragar said:
Is the B field constant inside a toroid?
Like we would just use amperes law to find.
B(2*pi*r)=(mu_0)NI
But after talking to this kid he said it changes inside. But i thought it was constant.

Where N is the numbers of turns ?
Didn't think the question was hard . Just not sure if s is fixed .

Its ok i figured it out . The field inside the toroid does vary with the radius, stronger on the inside edge and weaker on the outer edge .

## 1. What is a toroid?

A toroid is a three-dimensional shape in the form of a doughnut or a ring. It is created by rotating a circle around an axis that lies in the same plane as the circle. It is commonly used in electrical engineering and physics as a shape for inductors and transformers.

## 2. How is the B field inside a toroid calculated?

The B field inside a toroid can be calculated using the formula B = μNl / 2πr, where μ is the permeability of the material, N is the number of turns of wire, l is the length of the toroid, and r is the radius of the toroid. This formula takes into account the magnetic flux density, the number of turns of wire, and the geometry of the toroid.

## 3. What factors affect the B field inside a toroid?

The B field inside a toroid is affected by the permeability of the material, the number of turns of wire, and the geometry of the toroid. Other factors that may affect the B field include the current flowing through the wire, the frequency of the alternating current, and the presence of other magnetic fields in the surrounding environment.

## 4. Why is the B field inside a toroid considered to be uniform?

The B field inside a toroid is considered to be uniform because it is evenly distributed throughout the toroid's cross-sectional area. This is due to the circular shape of the toroid, which ensures that the distance from the center to any point on the cross-section is the same. This results in a constant B field strength throughout the toroid.

## 5. How does the B field inside a toroid compare to the B field outside the toroid?

The B field inside a toroid is much stronger than the B field outside the toroid. This is because the magnetic field lines are confined within the toroid, resulting in a higher concentration of field lines and a stronger overall field. The B field outside the toroid is significantly weaker and more spread out due to the absence of the toroid's shape and materials to concentrate the field lines.