Science (English Medium) Class 11 - CBSE Question Bank Solutions for Physics

The temperature of an object is observed to rise in a period. In this period

(a) heat is certainly supplied to it

(b) heat is certainly not supplied to it

(c) heat may have been supplied to it

(d) work may have been done on it

Heat and work are equivalent. This means, ____________ .

An electric bulb of volume 250 cc was sealed during manufacturing at a pressure of 10⁻³ mm of mercury at 27°C. Compute the number of air molecules contained in the bulb. Avogadro constant = 6 × 10²³ mol⁻¹, density of mercury = 13600 kg m⁻³ and g = 10 m s⁻².

Use R=8.314J K^-1 mol^-1

The density of an ideal gas is 1.25 × 10⁻³ g cm⁻³ at STP. Calculate the molecular weight of the gas.

Use R=8.31J K^-1 mol^-1

A resistance thermometer reads R = 20.0 Ω, 27.5 Ω, and 50.0 Ω at the ice point (0°C), the steam point (100°C) and the zinc point (420°C), respectively. Assuming that the resistance varies with temperature as R_θ = R₀ (1 + αθ + βθ²), find the values of R₀, α and β. Here θ represents the temperature on the Celsius scale.

A concrete slab has a length of 10 m on a winter night when the temperature is 0°C. Find the length of the slab on a summer day when the temperature is 35­°C. The coefficient of linear expansion of concrete is 1.0 × 10^–5 °C^–1.

Consider a sample of oxygen at 300 K. Find the average time taken by a molecule to travel a distance equal to the diameter of the earth.

Use R=8.314 JK^-1 mol^-1

A metre scale made of steel is calibrated at 20°C to give correct reading. Find the distance between the 50 cm mark and the 51 cm mark if the scale is used at 10°C. Coefficient of linear expansion of steel is 1.1 × 10^–5 °C^–1.

Find the ratio of the mean speed of hydrogen molecules to the mean speed of nitrogen molecules in a sample containing a mixture of the two gases.

Use R = 8.314 JK^-1 mol^-1

A railway track (made of iron) is laid in winter when the average temperature is 18°C. The track consists of sections of 12.0 m placed one after the other. How much gap should be left between two such sections, so that there is no compression during summer when the maximum temperature rises to 48°C? Coefficient of linear expansion of iron = 11 × 10^–6 °C^–1.

Figure shows a vessel partitioned by a fixed diathermic separator. Different ideal gases are filled in the two parts. The rms speed of the molecules in the left part equals the mean speed of the molecules in the right part. Calculate the ratio of the mass of a molecule in the left part to the mass of a molecule in the right part.

Estimate the number of collisions per second suffered by a molecule in a sample of hydrogen at STP. The mean free path (average distance covered by a molecule between successive collisions) = 1.38 × 10⁻⁵ cm.

Use R = 8.31 JK⁻¹ mol⁻¹

A circular hole of diameter 2.00 cm is made in an aluminium plate at 0°C. What will be the diameter at 100°C? α for aluminium = 2.3 ×  10^–5 °C^–1.

Hydrogen gas is contained in a closed vessel at 1 atm (100 kPa) and 300 K. (a) Calculate the mean speed of the molecules. (b) Suppose the molecules strike the wall with this speed making an average angle of 45° with it. How many molecules strike each square metre of the wall per second?

Use R = 8.31 JK^-1 mol^-1

A pendulum clock shows correct time at 20°C at a place where g = 9.800 m s^–2. The pendulum consists of a light steel rod connected to a heavy ball. It is taken to a different place where g = 9.788 m s^–1. At what temperature will the clock show correct time? Coefficient of linear expansion of steel = 12 × 10^–6 °C^–1.

The volume of a glass vessel is 1000 cc at 20°C. What volume of mercury should be poured into it at this temperature so that the volume of the remaining space does not change with temperature? Coefficients of cubical expansion of mercury and glass are 1.8 × 10^–6 °C^–1 and 9.0 × 10^–6 °C^–1 , respectively.

A vertical cylinder of height 100 cm contains air at a constant temperature. The top is closed by a frictionless light piston. The atmospheric pressure is equal to 75 cm of mercury. Mercury is slowly poured over the piston. Find the maximum height of the mercury column that can be put on the piston.

The densities of wood  and benzene at 0°C are 880 kg m³ and 900 kg m^–3 , respectively. The coefficients of volume expansion are 1.2 × 10^–3 °C^–1 for wood and 1.5 × 10^–3 °C^–1for benzene. At what temperature will a piece of wood just sink in benzene?

A steel rod of length 1 m rests on a smooth horizontal base. If it is heated from 0°C to 100°C, what is the longitudinal strain developed?