Question

An adult brain is about 140 mm wide, divided into two sections (called \"hemispheres\" although the brain is not truly spherical) each about 70 mm wide. We can model the current in one hemisphere as a circular loop, 65.0 mm in diameter, just inside the brain. The sensor is placed so that it is along the axis of the loop 2.50 cm from the center. A reasonable magnetic field is 4.35 fT at the sensor.

According to this model, what is the current in the brain?

What is the magnetic field at the center of the hemisphere of the brain?

Answer 1

30.40, Consider the hemispherical closed surface in Figure P30.40. If the hemisphere is in a uniform magnetic field that makes and angle theta with the vertical, calculate the magnetic flux through

(a) the flat surface S₁ and

= A B cos

A = R²

= R² B cos

(b) the hemispherical surface S₂.

According to Gauss's Law for magnetic flux, the total magnetic flux is zero. Since we know the flux coming into the surface ( = R² B cos ) that (or the negative) of that is also the flux coming out of the surface -- the flux through S₂,

= - R² B cos