Question

A straight wire of length $$0.5\,m$$  and carrying a current of $$1.2\,A$$  is placed in uniform magnetic field of induction $$2T.$$  The magnetic field is perpendicular to the length of the wire. The force on the wire is

A. $$2.4\,N$$
B. $$1.2\,N$$  
C. $$3.0\,N$$
D. $$2.0\,N$$
Answer :   $$1.2\,N$$
Solution :
Force on a current carrying conductor placed in a magnetic field is given by
$$F = i\left( {l \times B} \right) = il\,B\sin \theta $$
where, $$\theta =$$  angle between current elements and magnetic field.
If linear conductor carrying current is placed perpendicular to the direction of magnetic field, $$\left( {\theta = {{90}^ \circ }} \right)$$   it will experience maximum force.
i.e., $${F_{\max }} = ilB$$
Given, $$i = 1.2\,A,\,l = 0.5\,m\,\,{\text{and}}\,B = 2T$$
$$\therefore F = 2 \times 1.2 \times 0.5 = 1.2\,N$$

Releted MCQ Question on
Electrostatics and Magnetism >> Magnetic Effect of Current

Releted Question 1

A conducting circular loop of radius $$r$$ carries a constant current $$i.$$ It is placed in a uniform magnetic field $${{\vec B}_0}$$ such that $${{\vec B}_0}$$ is perpendicular to the plane of the loop. The magnetic force acting on the loop is

A. $$ir\,{B_0}$$
B. $$2\pi \,ir\,{B_0}$$
C. zero
D. $$\pi \,ir\,{B_0}$$
View Answer
Releted Question 2

A battery is connected between two points $$A$$ and $$B$$ on the circumference of a uniform conducting ring of radius $$r$$ and resistance $$R.$$ One of the arcs $$AB$$  of the ring subtends an angle $$\theta $$ at the centre. The value of the magnetic induction at the centre due to the current in the ring is

A. proportional to $$2\left( {{{180}^ \circ } - \theta } \right)$$
B. inversely proportional to $$r$$
C. zero, only if $$\theta = {180^ \circ }$$
D. zero for all values of $$\theta $$
View Answer
Releted Question 3

A proton, a deuteron and an $$\alpha - $$ particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If $${r_p},{r_d},$$  and $${r_\alpha }$$ denote respectively the radii of the trajectories of these particles, then

A. $${r_\alpha } = {r_p} < {r_d}$$
B. $${r_\alpha } > {r_d} > {r_p}$$
C. $${r_\alpha } = {r_d} > {r_p}$$
D. $${r_p} = {r_d} = {r_\alpha }$$
View Answer
Releted Question 4

A circular loop of radius $$R,$$ carrying current $$I,$$ lies in $$x - y$$  plane with its centre at origin. The total magnetic flux through $$x - y$$  plane is

A. directly proportional to $$I$$
B. directly proportional to $$R$$
C. inversely proportional to $$R$$
D. zero
View Answer

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Magnetic Effect of Current

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