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If all of the magnetic energy stored in this MRI magnet is converted to thermal energy, how much liquid helium will boil off? (a) 27kg ;(b) 38kg; (c) 60kg; (d) 110kg

Short Answer

Expert verified

The correct option is (c) 60kg

Step by step solution

01

Define magnetic energy and latent energy

Magnetic energy is the energy stored in magnetic materials due to moving charge carriers like electron. This magnetic energy is converted into latent thermal energy to boil off liquid helium. Latent heat of evaporation is the heat required to evaporate 1kg of liquid.

02

Calculation

Inductance of magnet,L=4,4Hz

Current, l=750A

Magnetic energy of magnet,

U=12Ll2U=12×4.4×7502U=1.237×106J

This magnetic energy is converted into heat and evaporate helium whose latent heat is20.9×103J/kg .

Q=mLm=QLm=1.237×10620.9×103m=60kg

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