12th Science Maharashtra Board
In this category students supposed to ask questions which belong to std 12th maharashtra board Science
- Prove that under certain conditions a magnet vibrating in uniform magnetic field performs angular S.H.M. Consider a bar magnet of magnetic moment μ, suspended horizontally by a light twistless fibre in a region where the horizontal component of... 1
- State the laws of simple pendulum. The period of a simple pendulum at a given place is T = 2π√(L/g) where L is the length of the simple pendulum and g is the acceleration due... 2
- Obtain the expression for the period of a simple pendulum performing S.H.M. An ideal simple pendulum is defined as a heavy point mass suspended from a rigid support by a weightless, inextensible and twistless string,... 1
- Using differential equation of linear S.H.M, obtain the expression for (a) velocity in S.H.M., (b) acceleration in S.H.M The general expression for the displacement of a particle in SHM at time t is x = A sin(ωt + α) ….. (1) where A and ω is a constant in a par... 2
- Define linear simple harmonic motion. Linear simple harmonic motion (SHM) is defined as the linear periodic motion of a body, in which the force (or acceleration) is always direc... 3
- The graph shows variation of displacement of a particle performing S.H.M. with time t. (B) The force is maximum at time 3T/4. 1
- Two identical springs of constant k are connected, first in series and then in parallel B) 1:2 The ratio of their frequencies of vertical oscillations will be in a ratio 1:2 1
- The length of second's pendulum on the surface of earth is nearly 1 m. Its length on the surface of moon should be A) 1/6 m Its length on the surface of moon should be 1/6 m 2
- A body of mass 1 kg is performing linear S.H.M. Its displacement x (cm) at t (second) is given by x = 6 sin (100t + p/ D) 18 J Maximum kinetic energy of the body is 18J 2
- A particle performs linear S.H.M. starting from the mean position. Its amplitude is A and time period is T. (A) √(3)/2A 1
- A hypothetical thermodynamic cycle is shown in the figure. Calculate the work done in 25 cycles. Given : a = fracΔV_max2=6-2/2×10⁻³m³ = 2 x 10⁻³ m³, b = fracΔP_max2=11-1/2×10⁵Pa = 5 x 10^(5 )Pa Cycles = 25 The work done in one cycle, oin... 1
- An ideal monatomic gas is adiabatically compressed so that its final temperature is twice its initial temperature. Given : T_f = 2T_i, monatomic gas ϒ = 5/3 P_iV_i^ϒ = P_fV_f^ϒ in an adiabatic process Now, PV= nRT ∴ V = nRT/P ∴ V_(i )= nRT_i/P_i and V_(f... 1
- An ideal gas is taken through an isothermal process. If it does 2000 J of work on its environment Given : W = 2000J , isothermal process In this case, the change in the internal energy of the gas, ΔU=0, as the gas is taken through an isot... 1
- A Carnot refrigerator operates between 250ºK and 300ºK. Calculate its coefficient of performance. Given : T_C = 250 K, T_H = 300 K K = T_C/T_H-T_C=250/300-250=250/50 = 5 this is the coefficient of performance of the refrigerator. 1
- Efficiency of a Carnot cycle is 75%. If temperature of the hot reservoir is 727ºC Given : η = 75% = 0.75, T_H = (273 + 727) K = 1000 K η = 1−T_C/T_H ∴ T_C/T_H= 1− η T_C = T_H (1 − η ) = 1000(1 - 0.75) = 250 K = (250 − 273)... 1
- A system releases 125 kJ of heat while 104 kJ of work is done on the system. Calculate the change in internal energy. Given: Q = −125kJ, W= −104kJ ΔU = Q − W= −125−(−104) = (−125 + 104) = −21kJ. Negative sign shows that decrease in energy. This is the change... 1
- A gas contained in a cylinder fitted with a frictionless piston expands against a constant external pressure of 1 atm Data: P = 1 atm = 1.013 x 10⁵ Pa, V₁ =5 litres =5 x 10⁻³ m³, V₂ = 10 Litres = 10 x 10⁻³ m³, Q = 400J. The work done by the system (gas in th... 1
- A mixture of hydrogen and oxygen is enclosed in a rigid insulting cylinder. It is ignited by a spark. The internal energy of a system is the sum of potential energy and kinetic energy of all the constituents of the system. In the example stat... 2
- Why should a Carnot cycle have two isothermal two adiabatic processes? With two isothermal and two adiabatic processes all reversible, the efficiency of the Carnot engine depends only on the temperatures of the... 1
- What sets the limits on efficiency of a heat engine? The temperature of the cold reservoir sets the limit on the efficiency of a heat engine. [Note: η = 1-T_C/T_H This formula shows that for ma... 1
- Give an example of some familiar process in which heat is added to an object, without changing its temperature. (a) Melting of ice (b) Boiling of water 2
- Give an example of some familiar process in which no heat is added to or removed form a system Answer: Any adiabatic process, for example the sudden bursting of a cycle tyre (air cools) or quickly compressing air in a bicycle pump (air... 1
- A gas contained in a cylinder surrounded by a thick layer of insulating material is quickly compressed. If a gas contained in a cylinder surrounded by a thick layer of insulating material is quickly compressed then (a) There is no transfer of h... 1
- During refrigeration cycle, heat is rejected by the refrigerant in the (A) condenser 2