While earning his PhD, Billy (yes, that Billy) did his experimental work using a cryostat equipped with a superconducting solenoid. When in use, the solenoid was immersed in a liquid helium bath (He is liquid at 4.2 K), this in turn allowed a (tunable) magnetic field within the superconducting solenoid as large as 8 tesla. Superconducting magnets typically have a rather high inductance (50 H), and operate at high currents for full field. As long as the solenoid remains superconducting, all is well, however should the solenoid quench or fall out of its superconducting state, a lot of energy is quickly released. Releasing a lot of energy into the liquid helium bath would result in that liquid quickly becoming a gas which would then occupy over 700 times the volume as the liquid form. This would not be a good thing, as asphyxiation could result.To avoid a quench, it is critical to keep the wires that make up the solenoid in their super- conducting state. To do this the solenoid is brought to full field (and tuned) very slowly. What constant voltage would need to be applied to raise the current from off to 150 volts in 2 hours.