IAT 1 PH8151 ENGINEERING PHYSICS PART A

Calculate the maximum deflection of a cantilever beam with udl(uniform distributed load) on entire span of 3m the intensity of you udl be 25 kN/m. Take EI as 4000 kN/m2.

• 0.052m

• 0.063m

• 0.076m

• 0.09m

Two wires have the same material and length, but their masses are in the ration of 4:3. If they are stretched by the same force, their elongations will be in the ratio of

• 2:3

• 3:4

• 4:3

• 9:16

The weight of a metal bar in water is 0.42 N and in air is 0.48, its density would be

• 8000 kg m-3

• 5000 kg m-3

• 6000 kg m-3

• 7000 kg m-3

A circular bar is subjected to an axial force and shear force, the difference between two principle stresses is 120 Mpa. Based on maximum shear stress theory what is the factor of safety, if elastic limit of the bar is 300 Mpa?

• 5

• 2

• 2.5

• 3

Principal stress of 30 Mpa and -70 Mpa acts on a material which has elastic limit stress in simple tension and compression as 60 Mpa and 200 Mpa respectively. Specify the reason for failure of the material assuming maximum principle stress theory

• Compression

• Tension

• Unpredictable

• None of the above

Following condition represents onset of necking

• εu = n

• εu = 1-n

• εu = 1+n

• εu = ln (1+n)

Change in elastic modulus for ordinary materials between 0K and melting point is

• 10-20% increase

• 10-20% decrease

• 80-90% decrease

• 80-90% increase

A He-Ne laser emits light of wavelength 632.8 nm and has a output power of 2.3 mW; then the number of photons emitted per second is

• 73.3 x 1014

• 29.56 x 1014

• 1173.5 x 1014

• 23.5 x 1014'

The total efficiency of an injection laser with GaAs active region is 12%. The applied voltage is 3.6 V and band gap energy for GaAs is 2.34 eV. Determine external power efficiency.

• 0.078

• 0.1

• 0.12

• 0.06

The external power efficiency of an injection laser with a GaAs is 13% having band gap energy of 1.64 eV. Determine external power efficiency.

• 0.198

• 0.283

• 0.366

• 0.467