1. Tardigrade
  2. Question
  3. Physics
  4. The emissivity and surface area of tungsten filament of an electric bulb are 0.35 and 0.25 × 10-4 metre 2 respectively. The operating temperature of filament is 3000 K. If σ=5.67 × 10-8 watt metre -2 K -4, then power of bulb is approximately:

Q. The emissivity and surface area of tungsten filament of an electric bulb are $0.35$ and $0.25 \times 10^{-4} metre ^{2}$ respectively. The operating temperature of filament is $3000\, K$. If $\sigma=5.67 \times 10^{-8}$ watt metre $^{-2} K ^{-4}$, then power of bulb is approximately:

Thermal Properties of Matter Report Error

Solution:

Given that
$e=0.35$
$A=0.25 \times 10^{-4} m ^{2}$
$\sigma=5.67 \times 10^{-8} Wm ^{-2} K ^{-4}$
$T=3000\, K$
We use $P=A e \sigma T^{4}$
$\Rightarrow P=0.25 \times 10^{-4} \times 0.35 \times 5.67 \times 10^{-8} \times(3000)^{4}$
$\Rightarrow P=40.2\, W$
$\Rightarrow P \approx 40\, W$

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

Latest Updates