Tag: temperature and heat

Quizzes (15) Questions (111)

Questions Related to temperature and heat

Multiple choice physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity
Metal floors cool more than a wood floor in winters because:

  1. Metal conducts heat more readily than wood

  2. Wood conducts heat more readily than metal

  3. Metal has a higher specific heat than wood

  4. The temperature of the wood is higher than the temperature of the metal

  5. The temperature of the metal is higher than the temperature of the wood
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Metals are good conductor of heat whereas wood does not conduct heat at all.

Thus in winters, metal floors cool more than a wood floor.

Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

Three rods of identical cross-sectional area and made from the same metal from the sides of an isosceles triangles ABC, right-angled at B. The point A and B are maintained at temperatures T and $(\sqrt{2})$T respectively. In the steady state, the temperature of the point C is $T _C$. Assuming that only heat conduction takes place, $T _C/T$ is?

  1. $\dfrac{1}{2\left(\sqrt{2}-1\right)}$

  2. $\dfrac{3}{\sqrt{2}+1}$

  3. $\dfrac{1}{\sqrt{3}\left(\sqrt{2}-1\right)}$

  4. $\dfrac{1}{\sqrt{2}+1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the steady-state heat flow condition (sum of heat currents at junction C is zero), the heat currents from A to C and B to C must balance. Given the geometry and thermal resistance, the calculation leads to the ratio 3/(sqrt(2)+1).

Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

If $K$ denotes coefficient of thermal conductivity, $d$ the density and $C$ the specific heat, the unit of $X$, where $X = K/dc$, will be

  1. $cm\space sec$

  2. $cm^2\space sec^{-2}$

  3. $cm \space sec^{2}$

  4. $cm^2 \space sec^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Units of the respective quantities in SI are:

  • $[K] = J(mKs)^{-1}$
  • $[\rho] = kg(m)^{-3}$
  • $[c] = J(kgK)^{-1}$
$[X] = \dfrac{[K]}{[\rho] [c]} = \dfrac{J(mKs)^{-1}}{(kg(m)^{-3})(J(kgK)^{-1})}$
$[X] = m^{2}s^{-1}$ or in CGS $cm^{2}s^{-1}$

Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

A body of length 1 m have an area of cross-section as 0.75 $m^{2}$. If rate of heat conduction of the body is 6000 J/s and coefficient of thermal conductivity is 200 $Jm^{-1}$ $K^{-1}$, then the temperature difference between the two ends of the body is

  1. $30^{\circ}C$

  2. $20^{\circ}C$

  3. $40^{\circ}C$

  4. $80^{\circ}C$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the formula Q/t = kA(dT/dx), where Q/t = 6000, k = 200, A = 0.75, and dx = 1. Rearranging gives dT = (Q/t * dx) / (kA) = (6000 * 1) / (200 * 0.75) = 6000 / 150 = 40 degrees C.

Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

Equal temperature difference exists between the ends of two metallic rods $1 $ and $2$ of length. Their thermal conductivities are $K _1$ and $K _2$ and cross sectional areas represents $A _1$ and $A _2$. The condition for equal rate of heat transfer is:

  1. $K _1A _2=K _2A _1$

  2. $K _1A _1=K _2A _2$

  3. $K _1A _1^2=K _2A _2^2$

  4. $K _1^2A _2=K _2^2A _1$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Equal temperature difference exists between the two metallic rods 1 and 2.
The heat transfer$=\dfrac{KA \Delta T}{l}$
For equal rate of heat transfer,
$\dfrac{K _1 A _1 \Delta T}{l}=\dfrac{K _2A _2 \Delta T}{l}$
$K _1A _1=K _2A _2$
The correct option is B.