Magnetic resonance imaging often need magnetic fields of a strength of around 1.50 T. The solenoid is 1.80 meters long and 75.0 cm in diameter. It is tightly wound with a single layer of 2.00 mm diameter superconducting wire. Required:
What current is needed?

The current needed is 2387.32 A

Explanation:

Given;

strength of the magnetic field, B = 1.5 T

length of the solenoid, L = 18 m

diameter of the solenoid, D = 75 cm = 0.75 m

diameter of the superconducting wire, d = 2 mm = 0.002 m

The number of turns of the solenoid is calculated as;

The magnetic field strength is given by;

Where;

I is the current needed

μ₀ is permeability of free space = 4π x 10⁻⁷ T.m/A

Therefore, the current needed is 2387.32 A

C) Pressure will compress a gas, reducing its volume and giving it a greater density and concentration of particles. Let's look at the available choices and determine why or why not they're correct. A) Pressure will expand a gas, enlarging its volume and reducing its density and concentration of particles. * What? So increasing the pressure on a gas will make it take up a larger volume? That definitely doesn't match the world I live in. I hope that's true for you as well. Wrong choice. B) Pressure will magnify a gas, developing its volume and multiplying its density and concentration of particles. * Lots of interesting sounding words, but they're mostly used in a nonsense fashion. Useful if you're easily fooled by technobabble, but it's another wrong answer. C) Pressure will compress a gas, reducing its volume and giving it a greater density and concentration of particles. * OK. Increasing the pressure will compress a gas. So it has a smaller volume. And since it still has the same mass, the density will become greater. And the particles closer together. Everything here matches reality. Good choice. D) Pressure will accelerate a gas, extending its volume and allowing a smaller density and concentration of particles. * Most technobabble. Why would the gas be accelerated? No reason that I know of. Wrong choice.