12th Science Maharashtra Board
In this category students supposed to ask questions which belong to std 12th maharashtra board Science
- Mention the conditions under which a real gas obeys ideal gas equation. A real gas obeys ideal gas equation when temperature is very high and pressure is very low. 1
- Explain, on the basis of kinetic theory, how the pressure of gas changes if its volume is reduced at constant temperatur The average kinetic energy per molecule of a gas is constant at constant temperature. When the volume of a gas is reduced at constant temper... 1
- When a gas is heated its temperature increases. Explain this phenomenon based on kinetic theory of gases. Molecules of a gas are in a state of continuous random motion. They possess kinetic energy. When a gas is heated, there is increase in the a... 1
- Define athermanous substances and diathermanous substances Athermanous substances- Substances that don't allow transmission of heat radiation through them are called athermanous substances. i.e. a su... 1
- If the density of oxygen is 1.44 kg/m3 at a pressure of 105 N/m2, find the root mean square Given : ρ = 1.44 kg/m^(3 ), P=10⁵ N/m² ∴ The root mean square velocity of oxygen molecules v_rms =√(3P/ρ) = √(3×10⁵/1.44) m/s = 4.564 × 10^(... 1
- Write ideal gas equation for a mass of 7 g of nitrogen gas. In the usual notation, PV =nRT. n= Mass of the gas/Molar Mass =7/28= 1/4 Therefore, the corresponding ideal gas equation is PV = 1/4 RT. 1
- On what factors do the degrees of freedom depend? The degrees of freedom depends upon the structure of the molecule the temperature of the gas. the number of atoms forming a molecule 1
- What will happen to the mean square speed of the molecules of a gas if the temperature of the gas increases? If the temperature of a gas increases, the mean square speed of the molecules of the gas will increase in the same proportion. V^(2 )= 3nRT/... 1
- The ratio of emissive power of perfectly blackbody at 1327° C and 527 °C is (A) 4:1 (B) 16 : 1 (C) 2 : 1 (D) 8 : 1 (B) 16 : 1 The ratio of emissive power of perfectly blackbody at 1327° C and 527 °C is 16 : 1 1
- If a = 0.72 and r = 0.24, then the value of tr is (A) 0.02 (B) 0.04 (C) 0.4 (D) 0.2 (B) 0.04 tr=1-a-r =1-0.72-0.24 =0.04 2
- If pressure of an ideal gas is decreased by 10% isothermally, then its volume will (A) decrease by 9% (B) increase (D) increase by 11.11% 2
- The mean free path λ of molecules is given by C) 1/√(2)πnd² 1
- i) In an ideal gas, the molecules possess (A) only kinetic energy (B) both kinetic energy and potential energy (A) only kinetic energy 2
- Why is the surface tension of paints and lubricating oils kept low? Answer: so that paints and lubricating oils spread easily and wet the surface well. A liquid with high surface tension tends to pull itself... 1
- In Bernoulli’s theorem, which of the following is conserved? (A) linear momentum (B) angular momentum (C) mass (D) energy In Bernoulli’s theorem, Energy is conserved 2
- Two hail stones with radii in the ratio of 1:4 fall from a great height through the atmosphere. (C) 1:16 Two hail stones with radii in the ratio of 1:4 fall from a great height through the atmosphere. Then the ratio of their terminal ve... 1
- The energy stored in a soap bubble of diameter 6 cm and T = 0.04 N/m is nearly (A) 0.9 × 10-3 J (B) 0.4 × 10-3 J (A) 0.9 × 10⁻³ J The energy stored in a soap bubble of diameter 6 cm and T = 0.04 N/m is nearly 0.9 × 10⁻³ J 1
- Two capillary tubes of radii 0.3 cm and 0.6 cm are dipped in the same liquid. B) 2:1 Two capillary tubes of radii 0.3 cm and 0.6 cm are dipped in the same liquid. The ratio of heights through which the liquid will rise... 1
- A hydraulic lift is designed to lift heavy objects of maximum mass 2000 kg. The area of cross section of piston (A) 0.8711 × 10⁶ N/m^(2 ) 2
- Find the radius of gyration of a uniform disc about an axis perpendicular to its plane and passing through its center Answer: K = R/√(2) ≈ 0.707 R The moment of inertia of a uniform disc of mass M and radius R about an axis through its centre and perpendicul... 1
- Give one property common to both hcp and ccp crystal lattices In hcp and ccp crystal lattices coordination number is 12 and packing efficiency is 74%. 1
- A rectangular wire frame of size 2 cm x 2 cm, is dipped in a soap solution and taken out. Answer: 3x10⁻⁵ J or 30μJ Explaination: A2=3x3=9 and A1= 2x2=4 Area are in cm² let convert it to m² A2=9x10⁻⁴ and A1=4x10⁻⁴ , T=3x10⁻² The ex... 1
- How much work is required to form a bubble of 2 cm radius from the soap solution having surface tension 0.07 N/m. Answer= 0.703× 10-3 J \ \ \ or \ \ \ 7.038× 10⁻⁴ J Explaination:: Given:: Radius of the bubble = 2 cm or 0.02 m Surface tension = 0.07 N/m S... 1
- A drop of mercury of radius 0.2 cm is broken into 8 droplets of the same size. Find the work done if the surface tension of mercury is 435.5 dyne/cm Answer:: 2.19 x 10⁻⁵ J Explaination:: Given :: R = 0.2 cm, n = 8, T = 435.5 dyn/cm As the volume of the liquid remains constant, volume of n... 1