Your Answer : (Not Answered)

Correct Answer : A

A rotary pump reaches about \(10^{-3}\) Torr.

An oil-sealed rotary (mechanical) pump works by trapping and compressing gas, and its ultimate pressure is typically \(10^{-2}\) to \(10^{-3}\) Torr, limited by back-leakage and the vapour pressure of its oil. It is used as a roughing and backing pump.

Pressures of \(10^{-6}\) Torr (high vacuum) need a diffusion or turbomolecular pump backed by a rotary pump, and \(10^{-10}\) Torr (ultra-high vacuum) needs ion, getter or cryogenic pumps with baking. 1 Torr is far worse than a working rotary pump achieves.

Your Answer : (Not Answered)

Correct Answer : C

The most suitable is the radiation pyrometer.

A radiation pyrometer measures temperature from the thermal radiation a hot body emits, using the Stefan-Boltzmann or Planck laws. It does not touch the body, so it has no upper limit set by the melting or failure of a sensor, and it is used for furnaces, molten metals and similar temperatures above 3000 °C.

A platinum resistance thermometer is limited to roughly 1000 °C or so, common thermocouples to well under 2000 °C (refractory ones to about 2300 °C), and a gas thermometer's bulb softens or melts long before 3000 °C.