A. A ferromagnetic material becomes paramagnetic above the ‘Curie temperature’
B. Permanent magnets are made of hard materials, whereas electromagnets require soft magnetic
materials
C. Soft magnetic materials (e.g., pure iron) have higher permeability and low hysterisis loss and
coercive forces
D. Tungsten steel and alnico are not hard magnetic materials
Related Mcqs:
- Pick out the wrong statement about the machinability of metals. Machinability of a metal ?
A. Decreases with increase in strain hardening tendencies
B. Decreases with increase in hardness, in general
C. Depend on the composition, microstructure and physical & mechanical properties
D. Decreases with increases in tensile strength & decrease in grain size - Pick out the wrong statement ?
A. Both annealing and normalising release the internal stresses of the material besides improving
the mechanical properties
B. Low carbon steel does not respond to the heat treatment for hardening of the material, hence it
is subjected to case hardening or surface hardening processes like cyaniding, carburising,
nitriding etc., which produces high carbon outer layers resulting in increase of surface
hardness
C. Induction hardening and flame hardening techniques are also used for surface hardening
D. Martempering of a material is a hardening process - Pick out the wrong statement?
A. Processing of thermosetting plastics is ideally done by injection moulding
B. Processing of thermoplastics is ideally done by compression moulding
C. Mass production of seamless pipes are done by electrical resistance welding (ERW)
D. Stretch forming is a process of cold drawing - Pick out the wrong statement ?
A. Seam welding, projection welding & spot welding are the classification of electrical resistance
welding
B. Electrode tip in spot welding is of copper and the tip diameter should be equal to t (where, t =
plate thickness to be welded)
C. In spot welding, two pieces to be joined are overlapped and placed between two electrodes
D. Mild steel sheet cannot be spot welded - Pick out the wrong statement ?
A. Lead can creep under its own weight at room temperature
B. The electrical conductivity of gold is considerably reduced by alloying additions due to the
decrease in electron movement
C. Recrystallisation temperature decreases with decrease in strain in a cold worked metal
D. With increase in temperature, the electrical conductivity of intrinsic semi-conductor will - Pick out the wrong statement ?
A. Molecules with symmetrical arrangements (e.g. CH4 or CCl4) are non-polar
B. Generally, non-polar compounds are chemically inactive, conduct electricity poorly and do
not ionise
C. Most of the hydrocarbons are non-polar
D. None of these - Pick out the wrong statement ?
A. The X-rays cannot be deflected by electric field unlike cathode rays
B. The intensity of X-rays can be measured by ionisation current produced due to the ionisation
of gas by X-rays
C. The quality of X-rays can be controlled by varying the anode-cathode voltage
D. Crystal structure of a material can be studied by an electron microscope - Pick out the wrong statement?
A. Ductile fracture of a stressed material, which exhibits a large plastic deformation is commonly
caused by the formation and coalescence of voids in the necked region
B. Brittle fracture is caused by the propagation of pre-existing cracks in the material and involves minimum plastic deformation
C. Fatigue fracture of a material is always brittle in nature and takes place due to the existence of
line imperfections
D. Brittle materials are generally tested in tension - Pick out the wrong statement about nucleate boiling ?
A. Bubble generation is by expansion of entrapped gas/vapour at small cavities in the surface
B. Surface temperature is greater than the saturation temperature of the liquid
C. Heat transfer from the surface of the liquid is less than that in film boiling
D. The temperature is less than that of film boiling - Pick out the wrong statement ?
A. The equivalent stiffness of two springs (of equal stiffness ‘S’) in series is S/2 while in parallel
is 2S
B. For a helical spring, deflection is proportional to D3 (D = mean coil diameter) or d4 (d = wire
diameter)
C. Crushing load or columns is less than the buckling load
D. Modulus of resilience is proportional to (stress at elastic limit)2
