Question

To generate a uniform 2T magnetic field for an MRI machine with a coil of diameter 50 cm and 10 000 turns over the 1 m distance of the coil,

(a) Solve for the current through the coil needed to create this large magnetic field.
(b) Approximate the total length of wire needed to produce 10 000 turns of this radius.
(c) If we need to keep the resistive power emitted by this coil under 1000 W so that the patient is not uncomfortable, what is the maximum resistance allowable by the coil?
(d) If the cross-sectional area of the wire used is 7.85×10^-9 m², find the maximum resistivity of wire that could be used to meet your criterion found in part (c).
(e) Copper has one of the lowest room temperature resitivities of all metals at ρ = 1.7×10^-8Ω m. Could an MRI machine with these requirements be made to operate with copper wire at room temperature as its coil? How is this avoided in real MRI machines?

Answer 1