For measuring the temperature of a red hot furnace, which is the most suitable instrument?

The root locus plot of the roots of the characteristics equation of a closed loop system having the open loop transfer function $$\frac{{{\text{K}}\left( {{\text{s}} + 1} \right)}}{{2\left( {2{\text{s}} + 1} \right)\left( {3{\text{s}} + 1} \right)}}$$    will have a definite number of loci for variation of K from 0 to $$\infty $$. The number of loci is

A. 1

B. 3

C. 4

D. 2

Phase lag of the frequency response of a second order system to a sinusoidal forcing function

A. Is 30°

B. Is 90° at the most

C. Approaches 180° asymptotically

D. Is 120°

Which of the following is not classified as a thermo electric pyrometer?

A. Resistance thermometer

B. Thermocouple

C. Optical pyrometer (disappearing filament type)

D. Radiation pyrometer

The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.

A. Chromel-alumel

B. Iron-constantan

C. Platinum-platinum/rhodium

D. None of these