Physics NCERT Exemplar Solutions Class 12th Chapter Four

${\overrightarrow{B}}_{Net}=\frac{{\mu }_0}{4\pi }*2\left[\frac{i_1}{d_1}-\frac{i_2}{d_2}\right]\left(-\widehat{k}\right)$

$=10^{-7}*2\left[\frac{4}{4}*100-\frac{2}{6}*100\right]\left(-\widehat{k}\right)$

$=2*10^{-5}\left[1-\frac{1}{3}\right]-\widehat{k}$

${\overrightarrow{B}}_{Net}=\frac{4}{3}*10^{-5}\left(-\widehat{k}\right)$                        

q = 3πc

$\overrightarrow{v}=2\widehat{i}+3\widehat{j}$

$\overrightarrow{F}=q\left(\overrightarrow{v}*\overrightarrow{B}\right)$               

= $3\pi \left[\left(2\widehat{i}*3\widehat{j}\right)*\frac{4}{3}*10^{-5}\left(-\widehat{k}\right)\right]$

$\overrightarrow{F}=4\pi *10^{-5}\left(-3\widehat{i}+2\widehat{j}\right)N$  

x = 3

Practicing the NCERT Exemplar problems helps in deepening the conceptual understanding of Chapter 4. These questions are designed to test the conceptual application and higher-order thinking. The solutions are given by the subject matter experts of Shiksha and practicing these strengthens the understanding of key topics like Biot–Savart law, magnetic forces, and Ampere's circuital law. It provides exam-oriented practice and students can score high in the CBSE Board exam and in entrance exams like NEET and JEE exams.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Explanation- for a charge particle to move in circular path

Mv²/r = qvB

v/r=w= bq/m

w= v/r = $\frac{L{T}^{-1}}{L}$ = T-1

This is a Multiple Choice Questions as classified in NCERT Exemplar

Explanation- force on charge particle due to both electric and magnetic field . now if electric force and magnetic field is zero then electric field and magnetic field is also zero.

Magnetic field is only responsible for constant velocity of charge particle if B=0 then E =0 if B is not equal to zero then electric field is also not equal to zero

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- (b, c)

Explanation- if current is in opposite sense the? Bdl = 0, also there exist a point where b and dl is perpendicular.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- (b, d)

Explanation- F=IlB, the direction of force is given by fleming's left hand rule and F is perpendicular to the direction of magnetic field. So work done is zero.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer – (a)

Explanation- gyro magnetic ratio does not depend upon which electron is rotating.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (d)

Explanation- W=MBcos $\theta$ , as the loop make 30 degree angle but angle made by axis of the loop with the direction of magnetic field, therefore work done is zero.