A coil with 100 turns is wound on a toroidal core as shown in Figure 5.15. The core has an inner radius of 2 cm, an outer radius of 5 cm, and a thickness of 1 cm. The
core material has a uniform permeability of μ = 200 μ0 and saturates at a flux density
of 1.2 T.
A What is the inductance of the coil?
B How much current is required to bring the core to the start of saturation (i. e. so that
the material at the inner diameter of the core reaches a flux density of 1.2 T)?
C How much current is required to fully saturate the core (i. e. to make all of the material in the core have a flux density of at least 1.2 T)?

Acommon procedure for measuring the velocity of an airstream involves the insertion of an electrically heated wire (called a hot-wire anemometer) into the airflow, with the axis of the wire oriented perpendicular to the flow direction. the electrical energy dissipated in the wire is assumed to be transferred to the air by forced convection. hence, for a prescribed electrical power, the temperature of the wire depends on the convection coefficient, which, in turn, depends on the velocity of the air. consider a wire of length l = 20 mm and diameter d = 0.5 mm, for which a calibration of the form v = 6.25 ă— 10â’5 h2 has been determined. the velocity v and the convection coefficient h have units of m/s and w/m2 â‹… k, respectively. in an application involving air at a temperature of tâž = 25â°c, the surface temperature of the anemometer is maintained at ts = 75â°c with a voltage drop of 5 v and an electric current of 0.1 a. what is the velocity of the air?