Home/Class 12/Physics/

Question and Answer

A negligibly small current is passed through a wire of length \(15\text { m}\)  and uniform cross-section \(6.0\times 10^{-7}\text{ m}^{2}\) , and its resistance is measured to be \(5.0\;\Omega \) . What is the resistivity of the material at the temperature of the experiment?


Here, we have length as \(15\text{ m}\) , area of \(6\times 10^{-17}\text{ m}^2\) and resistance as \(6\) ohms.
\(l=15\text{ m}\)
\(A=6\times 10^{-17}\text{ m}^2\)
To find the resistivity of the material, we use the following formula-
\(R=\rho \{\frac l A\}\)
\(5=\rho \left\{\frac{15} 6\right\}10^{17}\)
\(\rho =2\times 10^{-17}{\Omega-m}\)  .
To Keep Reading This Answer, Download the App
star pngstar pngstar pngstar pngstar png
Review from Google Play
To Keep Reading This Answer, Download the App
star pngstar pngstar pngstar pngstar png
Review from Google Play
Watch More Related Solutions
When a drop of oil is spread on a water surface, it displays beautiful colours in daylight because of
(a) dispersion of light
(b) reflection of light
(c) polarization of light
(d) interference of light
Four charges are arranged at the corners of a square \(\mathit{ABCD}\)  of side d. as shown in the figure. Find the work required to put together this arrangement.

A heating element using nichrome connected to a \(230\;V\) supply draws an initial current of \(3.2\) A which settles after a few seconds to a steady value of \(2.8\;A.\) What is the steady temperature of the heating element if the room temperature is \(27.0 °C\)? Temperature coefficient of resistance of nichrome averaged over the temperature range involved is \(1.70 \times 10-4 °C-1.\)
The index of refraction of fused quartz is \(1.472\) for light of wavelength \(400\;nm\) and is \(1.452\) for light of wavelength \(760\;nm\). Find the speeds of light of these wavelengths in fused quartz.
The earth’s surface has a negative surface charge density of \(10^{-9}\;\text{Cm}^{-2}\) . The potential difference of \(400\;\text{kV}\)  between the top of the atmosphere and the surface results \((\)due to the low conductivity of the lower atmosphere\()\) in a current of only \(1800\;\text A\)  over the entire globe. If there were no mechanism of sustaining atmospheric electric field, how much time \((\)roughly\()\) would be required to neutralise the earth’s surface? \((\)This never happens in practice because there is a mechanism to replenish electric charges, namely the continual thunderstorms and lightning in different parts of the globe, Radius of earth \(=6.37\times 10^6\;\text m)\) .
The percentage composition of carbon by mole in methane is ( )
A. \(75\%\)
B. \(20\%\)
C. \(25\%\)
D. \(80\%\)
Six lead-acid type of secondary cells each of emf \(2\text V\)  and internal resistance \(0.015\Omega \)  are joined in series to provide a supply to a resistance of \(8.5\Omega \) . What are the current drawn from the supply and its terminal voltage?
A secondary cell after long use has an emf of \(1.9\;\text V\)  and a large internal resistance of \(380\;\Omega \) . What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?
Choose the correct alternative:
Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.
Two wires \( A\) and \( B\), having identical geometrical construction, are stretched from their natural length by small but equal amount. The Young’s modulus of the wires are \( {Y}_{a}\) and \( {Y}_{b}\) whereas the densities are \( {\rho }_{a}\) and \( {\rho }_{b}\). It is given that \( {Y}_{a}>{Y}_{b}\) and \( {\rho }_{a}> {\rho }_{b}\). A transverse signal started at one end takes time \( {t}_{1}\) to reach the other end for \( A\) and \( {t}_{2}\) for \( B\)
(a) \( {t}_{1}\lt {t}_{2}\)
(b) \( {t}_{1} = {t}_{2}\)
(c) \(  {t}_{1}\gt {t}_{2}\)
(d) The information is insufficient to find the relation between \(t_1\) and \(t_2\).

Load More