In resistance heating highest working temperature is obtained from heating elements made of_____________?
(A) nickel copper
(B) nichrome
(C) silicon carbide
(D) silver
For heating element high resistivity material is chosen to______________?
(A) reduce the length of heating element
(B) increase the life of the heating element
(C) reduce the effect of oxidation
(D) produce large amount of heat
In the indirect resistance heating method, maximum heat-transfer takes place by____________?
(A) radiation
(B) convection
(C) conduction
(D) any of the above
For intermittent work which of the following furnaces is suitable ?
(A) Indirect arc furnace
(B) Core less furnace
(C) Either of the above
(D) None of the above
Induction heating takes place it which of the following ?
(A) Insulating materials
(B) Conducting materials which are magnetic
(C) Conducting materials which are non-magnetic
(D) Conducting materials which may or may not be magnetic
By which of the following methods the temperature inside arc nace can be varied ?
(A) By disconnecting some of the heating elements
(B) By varying the operating voltage
(C) By varying the current through heating elements
(D) By any of the above method
In induction heating ___________ is abnormally high?
(A) phase angle
(B) frequency
(C) current
(D) voltage
In a resistance furnace the atmosphere is_____________?
(A) oxidizing
(B) deoxidising
(C) reducing
(D) neutral
Which of the following has the highest value of thermal conductivity ?
(A) Water
(B) Steam
(C) Sold ice
(D) Melting ice
Heat transfer by condition will not occur when____________?
(A) bodies are kept in vacuum
(B) bodies are immersed in water
(C) bodies are exposed to thermal radiations
(D) temperatures of the two bodies are identical