**Chapter-4|Moving Charges and Magnetism| NCERT 12th Physics:**

**Toriod:**

The toroid is a hollow circular ring on which a large number of insulated turns of a metallic wire are closely wound.

Toroid is used in devices such as synchrotron in which high magnetic field is required.

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**Note: ** Since there is no current is flowing inside or outside the toroid so there is no magnetic field (outside or inside).

So we have to calculate magnetic field at point P only.

Let I be the current, r be the mean radius, n be the number of turns per unit length and B be the Magnetic field inside the toroid.

The line integral of magnetic field around closed path of circle of radius r is-

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**Force on Moving Charge in a Uniform Magnetic Field:**

In case of motion of charge in a magnetic field, the magnetic force is perpendicular to the velocity of the particle.

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