Tag: physics

Questions Related to physics

A piece of glass is heated to a high temperature and then allowed to cool. If it cracks, a probable reason for this is the following property of glass :

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. Low thermal conductivity

  2. High thermal conductivity

  3. High specific heat

  4. High melting point

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Correct Option: A
Explanation:

In case of low thermal conductivity, the heat is not distributed properly. When it is heated, the temperature at its outer  surface increases more than in the inner part. This means expansion on the outer part will be more than the inner part. So a stress will be generated. If the body is cooled again, the outer surface will contract more rapidly, then the inner part. This stress will generate crack in the body.

The apparent coefficient of expansion of a liquid depends upon :

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. the nature of the liquid

  2. the scale of temperature

  3. the mass of the liquid

  4. the pressure of the liquid

Show answer
Correct Option: C
Explanation:

The apparent coefficient of expansion of a liquid depends on the mass of the liquid.

Which of the following would expand more on heating?

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. Carbon dioxide

  2. Hydrogen peroxide

  3. Calcium hydroxide

  4. Calcium carbonate

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Correct Option: A
Explanation:

In room temperature, carbon dioxide is gas, hydrogen peroxide is liquid, calcium hydroxide is solid and calcium carbonate is solid.

Gases expand more because of large intermolecular distance and weak intermolecular force.

Wires on electric poles are mounted tightly, in winter.

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
As due to their linear coefficient of expansion
$\alpha =\cfrac { 1 }{ L } \cfrac { dL }{ dT } $
the wires will get a bit loose when summer comes, so they are safe. If they are loosely mounted in winters then as when summer comes, they will become more loose and can cause accidents.

While laying the railway tracks on wooden plank,a small gap is left between the successive lengths of rail because

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. It no gap is left, the expansion of rails will cause them to bend sideways

  2. If no gap is left, the expansion will break the rails

  3. If no gap is left, rails decrease in length

  4. All

Show answer
Correct Option: A
Explanation:

The rails of railway tracks are made up of steel.in summer,due to considerable rise in atmospheric temperature, the rails tend to increase in length,so they bend sideways if they are not allowed to increase in length.therefore while laying the railway tracks on wooden plank,a small gap is left between the successive lengths of rail.

Pouring hot water to open the tightly closed lid is an application of : 

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. Thermal expansion in liquid

  2. Thermal expansion in solid

  3. Thermal expansion in gas

  4. Thermal expansion in both solid and liquid

Show answer
Correct Option: B
Explanation:

When we pour hot water on a tightly closed lid, it expands due to heat gained from hot water. Due to this heat lid expands and becomes loose. This is thermal expansion of solids.

Why the telephone and electrical cables are strung out a little loose between the poles?

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. To transfer high voltage current.

  2. To prevent contraction and snapping of the wire during winter.

  3. To avoid confusion in connecting the wires

  4. To avoid congestion over poles

Show answer
Correct Option: B
Explanation:

When a solid gets heat it expands and on cooling it contracts. Due to this electrical and telephone cables are strung out a little loose so that in winter, as cables contract due to cooling of atmosphere and snapping may occur, can be avoided. 

There are two spherical balls A and B of the samematerial with same surface, but the diameter of A is half that of B. If Aand B are heated to the sametemperature and then allowed to cool, then 

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. Rate of cooling is same in both

  2. Rate of cooling of A is four times that of B

  3. Rate of cooling of A is twice that of $\mathrm { B }$

  4. Rate of cooling of A is 1$/ 4$ times that of $\mathrm { B }$

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Correct Option: C

why Loops are joined with the metal pipe line?

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. capacity

  2. temperature

  3. pressure

  4. none of these

Show answer
Correct Option: A
Explanation:

Metals has the capacity to expand or contract due to temperature change. Metals pipe also expand in summer and contract in winter, such changes can cause deformities, inorder to avoid this, loops are joined with the metal pipe.

A clock which keeps correct time at $20^{\small\circ}C$, is subjected to $40^{\small\circ}C$. If coefficient of linear expansion of the pendulum is $12\times10^{-6}$ per $^{\small\circ}C$. How much will it gain or loose in time?

physics heat and temperature anomalous expansion of water thermal expansion in solids, liquids and gases thermal expansion

  1. $10.3\space seconds/day$

  2. $20.6\space seconds/day$

  3. $5\space seconds/day$

  4. $20\space minutes/day$

Show answer
Correct Option: A
Explanation:

$\quad T = 2\pi\sqrt{\displaystyle\frac{l}{g}}$
$\quad \displaystyle\frac{\triangle T}{T} = 2\pi\times\displaystyle\frac{1}{2}(l/g)^{-1/2}\times\triangle l/l$
$\quad (\because T + \triangle T = 2\pi\sqrt{\displaystyle\frac{l+\triangle l}{g}})$
$\quad \therefore \displaystyle\frac{\triangle T}{T} = \displaystyle\frac{1}{2}\displaystyle\frac{\triangle l}{l} = \displaystyle\frac{1}{2}\propto\triangle\theta$
$\quad = \displaystyle\frac{1}{2}\times12\times10^{-6}\times(40-20) = 12\times10^{-5}$
$\quad \triangle T = T\times12\times10^{-5} = 24\times60\times60\times10^{-5} = 10.3\space s/day$