Two ideal solenoids of radii r and 6r, respectively, have n turns per meter and each carries a current i. both currents flow in the same direction. the small radius solenoid is placed inside the large radius solenoid so that their axes of symmetry are parallel and separated by a distance d = 3r . neglecting any magnetic screening effects, express anaytically the magnetic field strength on the axis of the small-radius solenoid in terms of the quantities given above and the magnetic permeability of a vacuum, %u03bc0.

tube or goog will be great resources to find the answer to the question that you're asking

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.

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

the answer is 12 as i may remember

: )