Q. Two identical rods of a metal are welded as shown in figure-4.39(a). $20\, cal$ of heat flows through them in $4$ minute. If the rods are welded as shown in figure-4.39(b), then the same amount of heat will flow in :

Thermal Properties of Matter Report Error

A

1 minute

B

2 minute

C

4 minute

D

16 minute

Solution:

As we use $20=\frac{k A(100-0) t_{1}}{2 L}$ ...(1)
$\Rightarrow 20=Q=\frac{k(2 A)(100-0) t_{2}}{L}$ ...(2)
$\Rightarrow \frac{t_{1}}{2}=2 t_{2}$
$\Rightarrow t_{2}=\frac{t_{1}}{4}=\frac{4}{4}=1\, \min$

Questions from Thermal Properties of Matter

1. If the temperature difference on the two sides of a wall increases from $100{}^\circ C$ to $200{}^\circ C$ , its thermal conductivity

Rajasthan PMT 2007

2. A wall is made of equally thick layers $A$ and $B$ of different materials. Thermal conductivity of $A$ is twice that of $B$ . In the steady state, the temperature difference across the wall is $36^{\circ}C$ . The temperature difference across the layer $A$ is

3. The radiation emitted by a star $A$ is $10,000$ times that of the sun. If the surface temperatures of the sun and the star $A$ are $8000 \, K$ and $2000 \, K$ respectively. The ratio of the radii of the star $A$ and the sun is

NTA Abhyas 2020

4. A black body at $1373$ $℃$ emits maximum energy corresponding to a wavelength of $1.78$ microns. The temperature of the moon for which $\lambda _{m}=14$ micron would be

NTA Abhyas 2020

5. Three rods made from the same material and having the same cross-sectional area, form the sides of an isosceles triangle $ABC$ , right-angled at $B$ . The points $A$ and $B$ are maintained at temperature $T$ and $\sqrt{2}T$ , respectively. In steady-state, the temperature of the point $C$ is $T_{C}$ . Assuming that only heat conduction takes place along the lengths of the rods, the value of $\frac{T_{C}}{T}$ is

NTA Abhyas 2020

Physics Most Viewed Questions

1. If $E$ and $G$ respectively denote energy and gravitational constant, then $\frac{ E }{ G }$ has the dimensions of:

NEET 2021 Physical World, Units and Measurements

2. The de Broglie wavelength of an electron moving with kinetic energy of $144 \,eV$ is nearly

NEET 2020 Dual Nature of Radiation and Matter

3. A car starts from rest and accelerates at $5\, m / s ^{2}$ At $t=4\, s$ , a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at $t =6\, s$ ? (Take $\left. g =10\, m / s ^{2}\right)$

NEET 2021 Motion in a Straight Line

4. A wheel with $20$ metallic spokes each $1\, m$ long is rotated with a speed of $120\, rpm$ in a plane perpendicular to a magnetic field of $0.4\, G$ . The induced emf between the axle and rim of the wheel will be, $(1 G = 10^{-4}\, T)$

NEET 2020 Electromagnetic Induction

5. A barometer is constructed using a liquid (density $= 760 \,kg/m^{3})$ What would be the height of the liquid column, when a mercury barometer reads $76\, cm$ ?
(density of mercury $= 13600 kg/m^{3})$

NEET 2020 Mechanical Properties of Fluids

Q. Two identical rods of a metal are welded as shown in figure-4.39(a). 20cal20\, cal of heat flows through them in 44 minute. If the rods are welded as shown in figure-4.39(b), then the same amount of heat will flow in :

1 minute

2 minute

4 minute

16 minute

As we use 20=kA(100−0)t12L20=\frac{k A(100-0) t_{1}}{2 L} ...(1) ⇒20=Q=k(2A)(100−0)t2L\Rightarrow 20=Q=\frac{k(2 A)(100-0) t_{2}}{L} ...(2) ⇒t12=2t2\Rightarrow \frac{t_{1}}{2}=2 t_{2} ⇒t2=t14=44=1min\Rightarrow t_{2}=\frac{t_{1}}{4}=\frac{4}{4}=1\, \min

Questions from Thermal Properties of Matter

1. If the temperature difference on the two sides of a wall increases from 100∘C 100{}^\circ C to 200∘C 200{}^\circ C , its thermal conductivity

2. A wall is made of equally thick layers AA and BB of different materials. Thermal conductivity of AA is twice that of BB. In the steady state, the temperature difference across the wall is 36∘C36^{\circ}C. The temperature difference across the layer AA is

3. The radiation emitted by a star AA is 10,00010,000 times that of the sun. If the surface temperatures of the sun and the star AA are 8000K8000 \, K and 2000K2000 \, K respectively. The ratio of the radii of the star AA and the sun is

4. A black body at 13731373 ℃℃ emits maximum energy corresponding to a wavelength of 1.781.78 microns. The temperature of the moon for which λm=14\lambda _{m}=14 micron would be

Physics Most Viewed Questions

1. If EE and GG respectively denote energy and gravitational constant, then EG\frac{ E }{ G } has the dimensions of:

2. The de Broglie wavelength of an electron moving with kinetic energy of 144eV144 \,eV is nearly

3. A car starts from rest and accelerates at 5m/s25\, m / s ^{2} At t=4st=4\, s, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at t=6st =6\, s ? (Take g=10m/s2)\left. g =10\, m / s ^{2}\right)

4. A wheel with 2020 metallic spokes each 1m1\, m long is rotated with a speed of 120rpm120\, rpm in a plane perpendicular to a magnetic field of 0.4G0.4\, G. The induced emf between the axle and rim of the wheel will be, (1G=10−4T)(1 G = 10^{-4}\, T)

5. A barometer is constructed using a liquid (density =760kg/m3)= 760 \,kg/m^{3}) What would be the height of the liquid column, when a mercury barometer reads 76cm76\, cm ? (density of mercury =13600kg/m3)= 13600 kg/m^{3})

Latest Updates

Q. Two identical rods of a metal are welded as shown in figure-4.39(a). $20\, cal$ of heat flows through them in $4$ minute. If the rods are welded as shown in figure-4.39(b), then the same amount of heat will flow in :

As we use $20=\frac{k A(100-0) t_{1}}{2 L}$ ...(1)
$\Rightarrow 20=Q=\frac{k(2 A)(100-0) t_{2}}{L}$ ...(2)
$\Rightarrow \frac{t_{1}}{2}=2 t_{2}$
$\Rightarrow t_{2}=\frac{t_{1}}{4}=\frac{4}{4}=1\, \min$

1. If the temperature difference on the two sides of a wall increases from $100{}^\circ C$ to $200{}^\circ C$ , its thermal conductivity

2. A wall is made of equally thick layers $A$ and $B$ of different materials. Thermal conductivity of $A$ is twice that of $B$ . In the steady state, the temperature difference across the wall is $36^{\circ}C$ . The temperature difference across the layer $A$ is

3. The radiation emitted by a star $A$ is $10,000$ times that of the sun. If the surface temperatures of the sun and the star $A$ are $8000 \, K$ and $2000 \, K$ respectively. The ratio of the radii of the star $A$ and the sun is

4. A black body at $1373$ $℃$ emits maximum energy corresponding to a wavelength of $1.78$ microns. The temperature of the moon for which $\lambda _{m}=14$ micron would be

1. If $E$ and $G$ respectively denote energy and gravitational constant, then $\frac{ E }{ G }$ has the dimensions of:

2. The de Broglie wavelength of an electron moving with kinetic energy of $144 \,eV$ is nearly

3. A car starts from rest and accelerates at $5\, m / s ^{2}$ At $t=4\, s$ , a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at $t =6\, s$ ? (Take $\left. g =10\, m / s ^{2}\right)$

4. A wheel with $20$ metallic spokes each $1\, m$ long is rotated with a speed of $120\, rpm$ in a plane perpendicular to a magnetic field of $0.4\, G$ . The induced emf between the axle and rim of the wheel will be, $(1 G = 10^{-4}\, T)$

5. A barometer is constructed using a liquid (density $= 760 \,kg/m^{3})$ What would be the height of the liquid column, when a mercury barometer reads $76\, cm$ ?
(density of mercury $= 13600 kg/m^{3})$