Question

A calorimeter of water equivalent $20 \mathrm{g}$ contains $180 \mathrm{g}$ of water at $25°\mathrm{C}$. ${}^{\text{'}}\mathrm{m}^{\text{'}}$' grams of steam at $100°\mathrm{C}$ is mixed in it till the temperature of the mixture is $31°\mathrm{C}$. The value of ${}^{\text{'}}\mathrm{m}^{\text{'}}$ is close to (Latent heat of water$=540 \mathrm{cal} {\mathrm{g}}^{-1}$, specific heat of water$=1 \mathrm{cal} {\mathrm{g}}^{-1°}{\mathrm{C}}^{-1}$)

JEE Main 2020 (03 Sep Shift 2)

Options

• A: $2$
• B: $4$
• C: $3.2$
• D: $2.6$

Question

Two thin metallic spherical shells of radii $r_1$ and $r_2\left(r_1<r_2\right)$ are placed with their centres coinciding. A material of thermal conductivity $K$ is filled in the space between the shells. The inner shell is maintained at temperature ${\theta }_1$ and the outer shell at temperature ${\theta }_2\left({\theta }_1<{\theta }_2\right).$ The rate at which heat flows radially through the material is :

JEE Main 2021 (31 Aug Shift 2)

Options

• A: $\frac{K\left({\theta }_2-{\theta }_1\right)}{r_2-r_1}$
• B: $\frac{K\left({\theta }_2-{\theta }_1\right)\left(r_2-r_1\right)}{4\pi r_1{r}_2}$
• C: $\frac{\pi K{r}_1{r}_2\left({\theta }_2-{\theta }_1\right)}{r_2-r_1}$
• D: $\frac{4\pi K{r}_1{r}_2\left({\theta }_2-{\theta }_1\right)}{r_2-r_1}$

Question

A rod $CD$ of thermal resistance $10.0{\mathrm{KW}}^{-1}$ is joined at the middle of an identical rod $AB$ as shown in figure. The ends $A, B$ and $D$ are maintained at $200°\mathrm{C},100°\mathrm{C}$ and $125°\mathrm{C}$ respectively. The heat current in $CD$ is $P \mathrm{W}$. The value of $P$ is

JEE Main 2021 (27 Aug Shift 1)

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Question

Two metallic blocks $M_1$ and $M_2$ of same area of cross-section are connected to each other (as shown in figure). If the thermal conductivity of $M_2$ is $K$ then the thermal conductivity of $M_1$ will be : [Assume steady state heat conduction]

JEE Main 2022 (24 Jun Shift 1)

Options

• A: $10K$
• B: $8K$
• C: $12.5K$
• D: $2K$

Question

A cylinder of fixed capacity of $44.8$ litres contains helium gas at standard temperature and pressure. The amount of heat needed to raise the temperature of gas in the cylinder by $20.0°\mathrm{C}$ will be (Given gas constant $R=8.3 \mathrm{J} {\mathrm{K}}^{-1} {\mathrm{mol}}^{-1}$)

JEE Main 2022 (29 Jun Shift 1)

Options

• A: $249 \mathrm{J}$
• B: $415 \mathrm{J}$
• C: $498 \mathrm{J}$
• D: $830 \mathrm{J}$

Question

At what temperature a gold ring of diameter $6.230 \mathrm{cm}$ be heated so that it can be fitted on a wooden bangle of diameter $6.241 \mathrm{cm}$? Both the diameters have been measured at room temperature $\left(27°\mathrm{C}\right)$.
(Given: coefficient of linear thermal expansion of gold ${\alpha }_L=1.4\times {10}^{-5}{ \mathrm{K}}^{-1}$)

JEE Main 2022 (29 Jun Shift 2)

Options

• A: $125.7°\mathrm{C}$
• B: $91.7°\mathrm{C}$
• C: $425.7°\mathrm{C}$
• D: $152.7°\mathrm{C}$

Question

A unit scale is to be prepared whose length does not change with temperature and remains $20 \mathrm{cm}$, using a bimetallic strip made of brass and iron each of different length. The length of both components would change in such a way that difference between their lengths remains constant. If length of brass is $40 \mathrm{cm}$ and length of iron will be _____ $\mathrm{cm}$.

$\left({\alpha }_{\mathrm{iron} }=1.2\times {10}^{-5}{ \mathrm{K}}^{-1}\right.$ and $\left.{\alpha }_{\mathrm{brass} }=1.8\times {10}^{-5}{ \mathrm{K}}^{-1}\right)$.

JEE Main 2022 (25 Jul Shift 1)

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Question

A steam engine intakes $50 \mathrm{g}$ of steam at $100°\mathrm{C}$ per minute and cools it down to $20°\mathrm{C}$. If latent heat of vaporization of steam is $540 \mathrm{cal} {\mathrm{g}}^{-1}$, then the heat rejected by the steam engine per minute is _____ $\times {10}^3 \mathrm{cal}$

(Given : specific heat capacity of water : $1 \mathrm{cal} {\mathrm{g}}^{-1}{{}^{\circ }\mathrm{C}}^{-1}$)

JEE Main 2022 (25 Jun Shift 1)

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Question

The graph between two temperature scales $P$ and $Q$ is shown in the figure. Between upper fixed point and lower fixed point there are $150$ equal divisions of scale $P$ and $100$ divisions on scale $Q$. The relationship for conversion between the two scales is given by :

.

JEE Main 2023 (25 Jan Shift 2)

Options

• A: $\frac{t_Q}{150}=\frac{{\displaystyle t_P-180}}{100}$
• B: $\frac{t_Q}{100}=\frac{{\displaystyle t_P-30}}{150}$
• C: $\frac{t_P}{180}=\frac{{\displaystyle t_Q-40}}{100}$
• D: $\frac{t_Q}{100}=\frac{{\displaystyle t_P-180}}{150}$

Question

$1 \mathrm{kg}$ of water at $100°\mathrm{C}$ is converted into steam at $100°\mathrm{C}$ by boiling at atmospheric pressure. The volume of water changes from $1.00\times {10}^{-3} {\mathrm{m}}^3$ as a liquid to $1.671 {\mathrm{m}}^3$ as steam. The change in internal energy of the system during the process will be (Given latent heat of vaporisation $=2257 \mathrm{kJ}/\mathrm{kg}$, Atmospheric pressure $\left.=1\times {10}^5 \mathrm{Pa}\right)$

JEE Main 2023 (11 Apr Shift 1)

Options

• A: $-2426 \mathrm{kJ}$
• B: $+2090 \mathrm{kJ}$
• C: $-2090 \mathrm{kJ}$
• D: $+2476 \mathrm{kJ}$

Question

A block of ice at $-10 °\mathrm{C}$ is slowly heated and converted to steam at $100 °\mathrm{C}$. Which of the following curves represent the phenomenon qualitatively:

JEE Main 2024 (30 Jan Shift 2)

Options

• A:
• B:
• C:
• D:

Question

Two conductors have the same resistances at $0 °\mathrm{C}$ but their temperature coefficients of resistance are ${\alpha }_1$ and ${\alpha }_2$. The respective temperature coefficients for their series and parallel combinations are :

JEE Main 2024 (31 Jan Shift 1)

Options

• A: ${\alpha }_1+{\alpha }_2, \frac{{\alpha }_1+{\alpha }_2}{2}$
• B: $\frac{{\alpha }_1+{\alpha }_2}{2}, \frac{{\alpha }_1+{\alpha }_2}{2}$
• C: ${\alpha }_1+{\alpha }_2, \frac{{\alpha }_1 {\alpha }_2}{{\alpha }_1+{\alpha }_2}$
• D: $\frac{{\alpha }_1+{\alpha }_2}{2}, {\alpha }_1+{\alpha }_2$