PH8151 Engg Physics Model Exam-2 Part-B

A 2.0 m long, 1.0 mm diameter wire is suspended from the ceiling. Hanging a 4.5 kg mass from the wire stretches the wire’s length by 1.0 mm. What is Young’s modulus for this wire?

• 220 GPa
•   22 GPa
• 110 GPa
•    11 GPa

A cantilever of rectangular cross-section has a length of 50 cm, breath of 3 cm and thickness of 0.6 cm. A weight of 1 kg is attached at the free end. The depression produced is 4.2 cm. Calculate Young’s modulus of the material of the rod.

• 18 Gpa
• 36 Gpa
• 27 Gpa
• 16 Gpa

Phase difference between oscillating medium and driven force at resonance condition is______ At same condition, amplitude of oscillation is ______.

• 0, maximum
• 𝜋/2, maximum
• 𝜋, maximum
• 2𝜋, maximum

In laser diode, optical resonator is

• combination of two <br />reflecting mirrors
• combination of one<br /> partially and one fully reflecting mirrors
• naturally cleaved <br />crystal planes
• one shine metal and <br />one transparent glass

A fiber cable has an acceptance angle of 30° and clading index of refraction 1.31. Calculate the refractive index of core.

• 1.31
• 1.4
• 1.23
• 1.38

Calculate the thickness of the slab of area 85 × 10−4m2 through which 8 joules of heat is flowing through the opposite faces maintained at a<br /> temperature difference of 30 K. The coefficient of thermal conductivity of the material of the slab is 0.05 Wm−1K−1. The time taken for the <br />heat flow is 12 seconds.

• 5 cm
• 3.8 cm
• 7.6 cm
• 1.9 cm

A uniform metallic rod of length L is fixed rigidly at two ends. When temperature of rod increases by ΔT, rod experiences thermal strain. If initial length of<br /> rod is 2L, the strain . For initial length of L, if temperature of rod increases by 2ΔT, the strain.

• is doubled; remains same
• remains same; is<br /> doubled
• remains same; <br />remains same
• is doubled; <br />is doubled

If two different materials of same length L and cross section A are connected in series manner, the heat current through the compound media is

• 𝑄 = 𝑑𝑇(𝐾1 + 𝐾2)/𝐴𝐿
• 𝑄 = 𝑑𝑇(𝐾1 + 𝐾2)𝐿/𝐴
• 𝑸 = 𝒅𝑻(𝑲𝟏 + 𝑲𝟐)𝑨/𝑳
• 𝑄 = 𝑑𝑇(𝐾1 + 𝐾2)𝐴𝐿

At what speed is an electron’s de Broglie wavelength 2.0 nm?

• 365 km/s
• 730 km/s
• 480 m/s
• 980 m/s

If monochromatic X-ray of wavelength 0.1 nm is scattered from a graphite target, minimum wavelength of scattered X-ray is

• 0.1240 nm
• 0.1480 nm
• 0.1 nm
• 0.076 nm