Tag: magnetic field due to a straight current carrying conductor

Questions Related to magnetic field due to a straight current carrying conductor

The Biot-Savart's law in vector from is:

  1. $ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { di\left( \overrightarrow { l } \times \overrightarrow { r } \right) }{ r^ 2 } $

  2. $ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { dl } \times \overrightarrow { r } \right) }{ r^ 2 } $

  3. $ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { r } \times \overrightarrow { dl } \right) }{ r^ 2 } $

  4. $ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { dl } \times \overrightarrow { r } \right) }{ r^ 3 } $


Correct Option: B

Which of the following particles will deviate $(< \pi/2)$ maximum when they enter magnetic filed region perpendicularly with same velocity and travel same distance.

  1. $He^{}$

  2. Proton

  3. $\alpha-particle$

  4. $Li^{++}$


Correct Option: D

A stationary magnet does not intereact with 

  1. iron rod

  2. moving charge

  3. moving magnet

  4. stationary charge


Correct Option: C

Which of the following gives the value of magnitude field according to, Biot-Savart's law'

  1. $ \frac {i\triangle l sin \theta}{r^2} $

  2. $ \frac {\mu _o}{4 \pi} \frac {i \triangle l sin \theta}{r} $

  3. $ \frac {\mu _o}{4\pi} \frac {i \triangle l sin \theta}{r^2} $

  4. $ \frac {\mu _o}{4 \pi} i \triangle l sin \theta $


Correct Option: C

The magnetic filed (dB) due to smaller element (dl) at a distance $(\vec r)$ from element carrying current i, is

  1. $\displaystyle dB = \frac{\mu _0 i}{4 \pi} \left ( \frac{\vec{dl} \times \vec r}{r} \right )$

  2. $\displaystyle dB = \frac{\mu _0 i}{4 \pi} i^2 \left ( \frac{\vec{dl} \times \vec r}{r^2} \right )$

  3. $\displaystyle dB = \frac{\mu _0 i}{4 \pi} i^3 \left ( \frac{\vec{dl} \times \vec r}{2r^2} \right )$

  4. $\displaystyle dB = \frac{\mu _0}{4 \pi} i \left ( \frac{\vec{dl} \times \vec r}{r^3} \right )$


Correct Option: D
Explanation:
$dB=\dfrac { { \mu  } _{ 0 }i }{ 4\pi  } \int { \dfrac { \left( \overrightarrow { dl } \times \hat { r }  \right)  }{ { r }^{ 2 } }  } \\$

we know that=$\hat { r } =\dfrac { \overrightarrow { r }  }{ { r }} \\$

$dB=\dfrac { { \mu  } _{ 0 }i }{ { 4 }\pi  } \int { \dfrac { \left( \overrightarrow { dl } \times \overrightarrow { r }  \right)  }{ { r }^{ 3 } }  }$ 

A particle of mass M and charge Q moving with velocity $\vec v$ describe a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. The work done by the field when the particle completes one full circle is

  1. $\displaystyle \left ( \frac{Mv^2}{R} \right ) 2 \pi R$

  2. $zero$

  3. $BQ2 \pi R$

  4. $BQv2 \pi R$


Correct Option: B
Explanation:

Upon completing a full circle net displacement is 0.
Work done by the magnetic field is 0 because the net displacement caused by the magnetic field is 0.

Assertion: Magnetism is relativistic

Reason: When we move along with the charge, so that there is no motion relative to us, we find no magnetic field associated with the charge

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true and R is not correct explanation of A.

  3. A is true, but R is false

  4. A is false, but R is true


Correct Option: A
Explanation:

A magnetic field is a region around some magnetic material or some moving electric charge. Within it the force of magnetism acts. Thus Magnetism is the aspect of the combined electromagnetic force. Also, it refers to the physical phenomena caused by magnets.

A magnetic field can be produced by the moving electric charge. As, the motion of any object is always relative, therefore the magnetic field will also be relativistic in nature.

As the reason is the correct explanation for the assertion

Hence option A is correct.

The magnetic field due to a current element is independent of :

  1. current through it

  2. distance from it

  3. its length

  4. nature of meterial


Correct Option: D
Explanation:

$B=\dfrac{\mu _o}{4\pi}\dfrac{i\overrightarrow{dl}\times\overrightarrow{r}}{r^3}$

So it depends on all three : current , distance and length
but not on nature of material

The magnetic field  $\overline{dB}$ due to a small current element dl at a distance $\vec{r}$ and carrying current ‘i’ is

  1. $\overline{dB}=\dfrac{\mu _{0}}{4\pi }i\left ( \dfrac{\overline{dl}\times \bar{r}}{r} \right )$

  2. $\overline{dB}=\dfrac{\mu _{0}}{4\pi }i^{2}\left ( \dfrac{\overline{dl}\times \bar{r}}{r^{2}} \right )$

  3. $\overline{dB}=\dfrac{\mu _{0}}{4\pi }i^{2}\left ( \dfrac{\overline{dl}\times \bar{r}}{r} \right )$

  4. $\overline{dB}=\dfrac{\mu _{0}}{4\pi }i\left ( \dfrac{\overline{dl}\times \bar{r}}{r^{3}} \right )$


Correct Option: D
Explanation:

Bio-savert law - apply directly the statement of law

Magnetic field at a point on the line of current carrying conductor is

  1. maximum

  2. infinity

  3. zero

  4. finite value


Correct Option: C
Explanation:

because angle between line and distance becomes zero.
$\therefore\overrightarrow{l}\times\widehat{r}$  becomes zero.