Why should an ammeter have a high current carrying capacity?

Why should a voltmeter have a low current carrying capacity?

Why should an ammeter have a low resistance?

Why should an ammeter have a low resistance and a high current carrying capacity?

Why should a voltmeter have a high resistance and a low current carrying capacity?

Why a population fluctuate when it reaches to carrying capacity ?

Why is it that the magnetic field of a current carrying coil having n turns, is 'n' times as large as that produced by a single turn (loop)?