Question

A charged particle moves through a magnetic field perpendicular to its direction. Then

A. kinetic energy changes but the momentum is constant
B. the momentum changes but the kinetic energy is constant  
C. both momentum and kinetic energy of the particle are not constant
D. both momentum and kinetic energy of the particle are constant
Answer :   the momentum changes but the kinetic energy is constant
Solution :
NOTE : When a charged particle enters a magnetic field at a direction perpendicular to the direction of motion, the path of the motion is circular. In circular motion the direction of velocity changes at every point (the magnitude remains constant).
Therefore, the tangential momentum will change at every point. But kinetic energy will remain constant as it is given by $$\frac{1}{2}m{v^2}$$  and $${v^2}$$ is the square of the magnitude of velocity which does not change.

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

Practice More MCQ Question on Physics Section

Basic PhysicsUnit and MeasurementKinematicsLaws of MotionFrictionUniform Circular MotionImpulseMomentumWork Energy and PowerRotational MotionGravitationMechanical Properties of Solids and Fluids
Heat and ThermodynamicsThermodynamicsThermal ExpansionConductionRadiationCalorimetryKinetic Theory of Gases
Electrostatics and MagnetismElectric ChargesElectric FieldElectric PotentialCapacitors and DielectricsMagnetic Effect of CurrentMagnetic MaterialsElectromagnetic WavesElectric CurrentElectromagnetic InductionAlternating CurrentSemiconductors and Electronic Devices
Optics and WaveRay OpticsWave Optics
Modern PhysicsDual Nature of Matter and RadiationAtoms And NucleiAtoms or Nuclear Fission and FusionRadioactivityModern Physics MiscellaneousSemiconductors and Electronic Devices
Oscillation and Mechanical WavesSimple Harmonic Motion (SHM)Waves