The ** magnetic field around** a wire is important to understand because it influences how energy is transferred and processed. The wire can carry an electric current, which is a flow of electrons.

When a wire carries an electric current, the moving electrons create a magnetic force. This force creates a *circular magnetic field around* the wire. The direction of the magnetic field is determined by the direction of the current in the wire.

The strength of the magnetic field around a wire carrying an electric current is proportional to two things: the length of the wire and the size of the current in the wire. This article will focus on how to calculate the magnitude of the **magnetic field 10 centimeters** from a 1 ampere (a) current.

This information will be useful for engineers and scientists who need to measure very small fields or need to know how strong a given field is for a given size and type of conductor.

## Calculate the area of the wire

Now that you know how to calculate the **magnetic field created** by a wire, you can calculate the area of the wire that *would create* a 1 A current through the wire for an hour.

The area of a circle is πr2, where r is the radius of the circle and π is 3.14. Therefore, the area of a circle is: A = πr2.

Since we are looking for an hour of *continuous current*, we will divide both sides by *60 minutes* to get: A = 1/60πr2.

## Convert meters to centimeters

The strength of the *magnetic field 10 centimeters away* from a wire carrying a 1 ampere (A) current is 2 milliteslas (mT).

This measurement is **also called gamma**. Millitesla is the SI unit for **measuring magnetic field strength**. One millitesla is equal to one thousandth of a tesla.

One tesla is equal to **one newton per ampere per meter**. The newton is the unit of force, and the ampere is the unit of electric current, so this unit measures how strongly the electricity moves through a given length of wire.

Gamma is an older SI unit that has been superseded by the tesla, but it still has some practical applications in industry standards.

One gamma is equal to 100 nanoteslas (nT), or 100000 gamma.

## Calculate the length of the wire

Now let’s calculate the length of the wire. We will use our answer from the **previous question**: The **magnetic field 10 cm** from a wire carrying a 1 a current is 2 μt.

We will divide both sides by 1 ampere, then we will get the length of the wire in meters. 1 A ÷ 1 m/s = 1 m Therefore, the length of the wire is 1 m.

We know that there are 1000 meters in a kilometer, so we will multiply our answer by 1000 to get the length of the wire in kilometers. 1 m × 1000 = 1000 m The length of the wire is one kilometer!

This is an important measurement, as it determines how *many loops* you can fit into your cage before running out of space.

## Determine whether or not the wire is round

Once you have determined that the wire is a wire and not a straight piece of metal, you must determine if it is round.

A round wire has two properties that affect your * magnetic field measurement*: the number of turns of the wire and the diameter of the wire. The more turns, the higher the magnetic field you will measure; the

**larger diameter wire**, the higher the magnetic field you will measure.

To determine if the wire is round, first measure its length and then its width. If these two numbers are close to each other, then it is probably round. If these two numbers are far apart, then it is probably not round.

After determining whether or not it is round, you must now determine how many turns it has. To do this, pull some of the wire apart and count how many times it *wraps around something* before returning to its original position.

## Calculate the radius of the wire

The final step in calculating the size of a wire is to calculate the radius of the wire. The formula for the radius of a wire is the diameter of the wire divided by twice the number of winds.

For example, if you have a *24 gauge wire* and you have two winds, then your radius would be 2/10 inches, or 0.2 feet. This is because you *would take* the diameter of the wire (0.024 inches) and divide that by *two times* the number of winds (2).

You can also use this formula with millimeters instead of inches. The only thing you need to change is the decimal point to a millimeter one!

This is an important thing to know when buying materials for your coil, as too thin of a coil may not form a *complete circle due* to its thin radius.

## Find the magnetic permeability of air

Next, you need to find the permeability of air. You already have the permeability of a wire, but you need to know how far away from the wire you are measuring.

Air has a constant thickness, so you just need to measure the distance from the wire to that thickness. Then you can use these formulas to find the permeability of air.

You will need to use a **unit conversion however**, as the formula only accepts SI units. You will convert millimeters into centimeters, and meters into kilometers. Then you can perform the calculation and get an answer!

Once you have found the permeability of air, you can return to calculating the *magnetic field* at a given distance from a wire carrying a *given current*.

## Find the number of wavelengths in the wire

Now let’s figure out how ** many wavelengths fit** into the wire. We’ll do this by finding how many wavelengths fit into the length of the wire.

We know the wavelength is 10 cm, so we just need to figure out how long the wire is. We can do this by dividing the wavelength by 2π, which gives us a length of 0.5 meters.

We also need to find how many half-wavelengths fit in that length. To do that, divide 2π by the wavelength, which **gives us 4π**/10 or 4half-wavelengths in the length of the wire.

Now we have to find how many half-wavelengths fit in 1 meter of wire. To do that, divide 4half-wavelengths by 0.5 meters, which **gives us 8 wavelengths per meter** of wire.

## Convert nanometers to millimeters

The strength of the magnetic field 10 cm from a wire carrying a 1 amp current is 2 mm. That is pretty close to millimeter, so you could just say the magnetic field is 2 mm from the wire.

Converting nanometers to millimeters is useful because it gives a sense of how far the influence of the wire goes.

We know that **stronger currents produce stronger magnetic fields**, so knowing how far the influence of the **current reaches allows us** to predict how strong the magnetic field will be at other distances.

We also know that **thicker wires produce stronger magnetic fields**, so again, knowing how far the influence of the **wire reaches allows us** to predict how strong the magnetic field will be at other distances.

This is helpful when determining how to deflect or shield against such fields.