Question

A charge $$q$$ moves in a region where electric field $$E$$ and magnetic field $$B$$ both exist, then the force on it is

A. $$q\left( {v \times B} \right)$$
B. $$qE + q\left( {v \times B} \right)$$  
C. $$qB + q\left( {B \times v} \right)$$
D. $$qB + q\left( {E \times v} \right)$$
Answer :   $$qE + q\left( {v \times B} \right)$$
Solution :
If $$E$$ is the electric field strength and $$B$$ is the magnetic field strength and $$q$$ is the charge on a particle, then electric force on the charge
$${F_e} = qE$$
and magnetic force on the charge
$${F_m} = q\left( {v \times B} \right)$$
The net force on the charge
$$F = {F_e} + {F_m} = qE + q\left( {v \times B} \right)$$
Alternative
According to Lorentz force if a charged particle is in both electric field $$\left( E \right)$$  and magnetic field $$\left( B \right),$$  force is given by
$$F = q\left[ {E + \left( {v \times B} \right)} \right]$$

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

Practice More Releted MCQ Question on
Magnetic Effect of Current

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