A circular coil has a 10.0 cm radius and consists of 30 closely wound turns of wire. An externally produced magnetic field of 2.6 mT is perpendicular to the plane of the coil.
(a) if there is no current in the loop, what is the magnetic flux through the coil?
(b) When the current in the coil is 3.8 A in certain direction, the net flux through the coil is found to vanish. What is the inductance of the coil

(a) 0.00245 Wb

(b) 0.000645 H

Explanation:

(a) The magnetic flux, Ф, through a coil of radius, r, having N turns due to a magnetic field, B, is given as:

Ф =

where A = area of coil =

Ф = NB

Ф =

Ф = 0.00245 Wb or

(b) If the magnetic flux through the coil vanishes, the magnetic flux due to the coil will be:

Ф =

where L = inductance in the coil and I = current in the coil

Therefore:

L = Ф/I

L = 0.00245/3.8

L = 0.000645 H or

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

because if the tool that you are using is not balanced it there would be false mass.