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**Magnetic field** - Wikipedia

A **magnetic field** is a vector field that describes the magnetic influence on moving
electric charges, electric currents, ^{:ch1} and magnetized materials. A charge that ...

For more information, see **Magnetic field** - Wikipedia

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Introduction to **magnetism** (video) | Khan **Academy**

An introduction to **magnetism**. ... **Magnetic force** on a **current carrying wire** ...
When a bar **magnet** is broken in the **middle**, what is the effect on its intensity? ...
In this time, the Earth's **magnetic field** automatically aligned the domains, or
atoms, of the ... **charge**) or changing **electric fields** and create **force** on **moving**
**charges** only.

For more information, see Introduction to **magnetism** (video) | Khan **Academy**

Given that

Coil radius = R

Number of turns = N

Current = I

Distance between magnetic field and centre = x

(a) Show that this reduces to the familiar result for field at the centre of the coil.

Magnetic field B = \frac{\mu _0 I R^2 N}{2(x^2 + R^2)^{\frac{3}{2}}}

Magnetic field at centre x = 0

B=\frac{\mu_0IR^2N}{2\left(0^2+\ R^2\right)^{\frac{3}{2}}}

B = \frac{\mu _0 I R^2 N}{2R^3}

B = \frac{\mu _0 I N}{2R}

Hence, B reduces to the familiar result for field at the centre of the coil