The rule that is used to get the strength of magnetic field at the center of solenoid (B) is:
B = <span>µ x n x I where:
</span>µ is the permeability of the medium where the solenoid is based. In this problem, the medium is air which means that µ = <span>µ </span><span>o = 4 pi x 10^-7 Tm/A
</span>I is the current passing (I = 4 amperes)
n is the number of turns per unit length (5000 turns)
Substituting in the mentioned equation, we find that:
B = 4 x 3.14 x 10^-7 x 5000 x 4 = 25.132 mT
It is durable because it is one of the strongest metals and doesn't corrode easily.
Possibly A. after all, the grid transmission system was designed at a time when electricity was generated using burning coal to heat water to steam to drive massive electrical dyamos which fed the grid which fed the houses.
Wind needs the weather to be windy.
Solar cells need some sunshine
tidal power needs coastal areas and very large areas at that.
