Weak magnetic fields can be measured at the surface of the brain. although the currents causing these fields are quite complicated, we can estimate their size by modeling them as a current loop around the equator of a 16-cm-diameter (the width of a typical head) sphere. what current is needed to produce a 3.0 pt field - the strength measured for one subject - at the pole of this sphere? (i = units).

1.08 × 10⁻⁶ A

Explanation:

Data provided in the question:

Diameter of the sphere, d = 16 cm

Magnetic field, B = 3.0 pT = 3 × 10⁻¹² T

now,

here,

z is the point of consideration i.e pole of the sphere from the center

= 16 ÷ 2 = 8 cm

permeability constant = μ₀ = 4π × 10⁻⁷ H/m

I is the current

on substituting the respective values, we get

3 × 10⁻¹² T =

or

3 × 10⁻¹² T =

or

I = 1.08 × 10⁻⁶ A

earth's neighboring galaxy, the andromeda galaxy, is a distance of 2.54×107 light-years from earth. if the lifetime of a human is taken to be 70.0 years, a spaceship would need to achieve some minimum speed min to deliver a living human being to this galaxy.