Consider a long, straight wire of cross-sectional area A carrying… - Vidyadip

MCQ

Consider a long, straight wire of cross-sectional area A carrying a current i. Let there be n free electrons per unit volume. An observer places himself on a trolley moving in the direction opposite to the current with a speed $\text{v}=\frac{\text{i}}{\text{nAe}}$ and separated from the wire by a distance r. The magnetic field seen by the observer is very nearly:

✓
$\frac{\mu_0\text{i}}{2\pi\text{r}}$
B
$\text{Zero}$
C
$\frac{\mu_0\text{i}}{\pi\text{r}}$
D
$\frac{2\mu_0\text{i}}{\pi\text{r}}.$

✓

Answer

Correct option: A.

$\frac{\mu_0\text{i}}{2\pi\text{r}}$

Magnetic field will be independent of the motion of the observer because the velocity with which the observer is moving is comparable to drift velocity of electron which is very small as compared to the speed of flow of current from one end of wire to other end. So it can be neglected and hence, magnetic field due to the wire w.r.t the observer will be $\text{B}=\frac{\mu_0\text{i}}{2\pi\text{r}}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from Magnetic Field due to a Current→Magnetic Field due to a Current — all question types→Physics STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

Which of the accompanying $PV$, diagrams best represents an isothermal process

Given below are two statements :

Statement $(I)$ : The mean free path of gas molecules is inversely proportional to square of molecular diameter.

Statement $(II)$ : Average kinetic energy of gas molecules is directly proportional to absolute temperature of gas.

In the light of the above statements, choose the correct answer from the option given below:

The coefficient of linear expansion depends on

A tuning fork produces $4\text{beats/ sec}$ with another fork of frequency $288\ \text{c.p.s}$. A little wax is placed on the unknown fork and it then produces $2\text{beats/ sec.}$ The unknown frequency is:

A ring and a solid sphere roll down the same inclined plane without slipping. They start from rest. The radii of both bodies are identical and the ratio of their kinetic energies is $\frac{7}{\mathrm{x}}$ where $\mathrm{x}$ is___________.

A proton exerts a force on a proton which is:

A spherical bubble inside water has radius $R$. Take the pressure inside the bubble and the water pressure to be $p_0$. The bubble now gets compressed radially in an adiabatic manner so that its radius becomes $(R-a)$. For $a \ll R$ the magnitude of the work done in the process is given by $\left(4 \pi p_0 R a^2\right) X$, where $X$ is a constant and $\gamma=C_p / C_V=41 / 30$. The value of $X$ is. . . . . .

A particle of mass $m$ moving with a velocity $v$ strikes a stationary particle of mass $2m$ and stickes to it. The speed of the system will be,

If $C$ and $L$ denote capacitance and inductance respectively, then the dimensions of $LC$ are

Following are the graphs of elastic materials. Which one corresponds to that of brittle material?