A single-turn circular loop of radius 6 cm is to produce a field at its center that will just cancel the earth's field of magnitude 0.7 G directed at 70 below the horizontal north direction. Find the current in the loop.

Respuesta :

Answer:

The current is  [tex]I = 6.68 \ A[/tex]

Explanation:

From the question we are told that  

     The radius of the loop is  [tex]r = 6 \ cm = 0.06 \ m[/tex]

     The  earth's magnetic field is [tex]B_e = 0.7G= 0.7 G * \frac{1*10^{-4} T}{1 G} = 0.7 *10^{-4} T[/tex]

      The  number of turns is  [tex]N =1[/tex]

Generally the magnetic field generated by the current in the loop is mathematically represented as

        [tex]B = \frac{\mu_o * N * I}{2 r }[/tex]

Now for the earth's magnetic field to be canceled out the magnetic field generated by the loop must be equal to the magnetic field out the earth

         [tex]B = B_e[/tex]

=>     [tex]B_e = \frac{\mu_o * N * I }{ 2 * r}[/tex]

     Where  [tex]\mu[/tex] is the permeability of free space with value  [tex]\mu _o = 4\pi * 10^{-7} N/A^2[/tex]

       [tex]0.7 *10^{-4}= \frac{ 4\pi * 10^{-7} * 1 * I}{2 * 0.06}[/tex]

=>     [tex]I = \frac{2 * 0.06 * 0.7 *10^{-4}}{ 4\pi * 10^{-7} * 1}[/tex]

       [tex]I = 6.68 \ A[/tex]

The current in the loop will be "6.68 A".

Magnetic field

According to the question,

Radius of loop, r = 6 cm or,

                           = 0.06 m

Earth's magnetic field, [tex]B_e[/tex] = 0.7 G or,

                                          = 0.7 × [tex]\frac{1\times 10^{-4}}{1 G}[/tex]

                                          = 0.7 × 10⁻⁴ T

Number of turns, N = 1

We know the relation,

→ B = [tex]\frac{\mu_0\times N\times I}{2r}[/tex]

or,

  B = [tex]B_e[/tex]

then,

→         [tex]B_e[/tex] = [tex]\frac{\mu_0\times N\times I}{2r}[/tex]

By substituting the values,

0.7 × 10⁻⁴ = [tex]\frac{4 \pi\times 10^{-7}\times 1\times I}{2\times 0.06}[/tex]  

hence,

The current will be:

               I = [tex]\frac{2\times 0.06\times 0.7\times 10^{-4}}{4 \pi\times 10^{-7}\times 1}[/tex]

                 = 6.68 A

Thus the above approach is correct.    

             

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