Expansion — Set 1
Physics · प्रसार · Questions 1–10 of 40
The coefficient of linear expansion of a solid is defined as?
Correct Answer: C. Fractional change in length per unit rise in temperature
Linear expansion coefficient tells how much length changes per degree. It equals (change in length)/(original length × temperature change). It is usually treated constant for a small temperature range.
For an isotropic solid, the coefficient of superficial expansion (β) is approximately?
Correct Answer: B. β = 2α
In isotropic solids, area expands in two perpendicular directions. So the superficial expansion coefficient is about twice the linear coefficient. This relation is valid for small temperature changes.
The SI unit of the coefficient of linear expansion is?
Correct Answer: A. K^-1
Coefficient of linear expansion represents change per unit temperature. So its unit must be the inverse of temperature. In SI, it is per kelvin (K^-1).
The correct formula for linear expansion is?
Correct Answer: A. ΔL = αLΔT
Linear expansion is directly proportional to original length and temperature rise. The proportionality constant is α. Therefore ΔL = αLΔT.
For an isotropic solid, the coefficient of cubical expansion (γ) is approximately?
Correct Answer: C. γ = 3α
Volume expansion happens along three independent dimensions. So cubical expansion coefficient is about three times the linear coefficient. This is a good approximation for small temperature changes.
A circular hole is cut in a metal plate. When the plate is heated uniformly, the diameter of the hole?
Correct Answer: A. Increases
The material around the hole expands outward on heating. The hole behaves as if it were made of the same material. So the hole’s diameter increases with temperature.
The apparent expansion of a liquid in a container is mainly because?
Correct Answer: B. The container also expands along with the liquid
A liquid truly expands when heated, called real expansion. The container also expands, increasing available volume. So the observed or apparent expansion is less than the real expansion.
Which statement about water between 0°C and 4°C is correct?
Correct Answer: C. It contracts and becomes denser
Water shows anomalous behavior from 0°C to 4°C. In this range, it contracts on heating and density increases. Water has maximum density at about 4°C.
A bimetallic strip is commonly used in?
Correct Answer: A. Thermostats and automatic switches
Two metals expand by different amounts when heated. This makes the strip bend in a predictable way. That bending is used to open or close electric contacts in thermostats.
Gaps are provided between railway rails mainly to?
Correct Answer: B. Allow expansion in hot weather
Metal rails expand when temperature rises. If there were no gaps, large compressive forces could build up. Gaps prevent bending or buckling due to thermal expansion.