G You are near a long straight current-carrying wire, and you measure the magnetic field due to the current in the wire at a location a distance d from the wire. If you move to a point 2d away from the wire and measure the magnetic field due to the current in the long straight wire, how will the magnitude compare to the field d away from the wire

B_2 / B_1 = 0.5 , Half of magnetic field at distance d.

Explanation:

Given:

- A current carrying conductor produces a magnetic field = B_1  @ r = d

- A current carrying conductor produces a magnetic field = B_2  @ r = 2*d

Find:

Compare the the magnetic Field at two points r = d and r = 2*d:

Solution:

- The magnetic Field of long current carrying wires are expressed as follows:

                                      B = u_o*I / 2*pi*r

Where,

B = Magnetic Field

I = The current in the conductor

r = The radial distance from the center of the wire.

u_o = Permittivity of free space (constant)

- Now compute B_1 and B_2:

                                    B_1 =   B = u_o*I / 2*pi*d

                                    B_2 =   B = u_o*I / 4*pi*d

- Take a ratio of B_2 to B_1:

                                    B_2 / B_1 = (u_o*I / 4pi*d) * ( 2*pi*d/u_o*I)

                                    B_2 / B_1 = 0.5

- Hence, the magnetic field at distance 2d is half of the magnetic field at distance d.

probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop