Join WhatsApp Icon JEE WhatsApp Group
Question 48

1 $$\mu$$C charge moving with velocity $$\vec{v} = \left(\hat{i} - 2\hat{j} + 3\hat{k}\right)$$ m/s in the region of magnetic field $$\vec{B} = \left(2\hat{i} + 3\hat{j} - 5\hat{k}\right)$$ T. The magnitude of force acting on it is $$\sqrt{\alpha} \times 10^{-6}$$ N. The value of $$\alpha$$ is __________.


Correct Answer: 171

The magnetic (Lorentz) force on a moving point charge is given by
$$\vec{F}=q\,\bigl(\vec{v}\times\vec{B}\bigr)$$

Given data:
Charge, $$q = 1\;\mu\text{C} = 1\times10^{-6}\,\text{C}$$
Velocity, $$\vec{v}=1\,\hat{i}-2\,\hat{j}+3\,\hat{k}\;(\text{m s}^{-1})$$
Magnetic field, $$\vec{B}=2\,\hat{i}+3\,\hat{j}-5\,\hat{k}\;(\text{T})$$

First, calculate the cross product $$\vec{v}\times\vec{B}$$.

Using the determinant form:
$$ \vec{v}\times\vec{B} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k}\\ 1 & -2 & 3\\ 2 & 3 & -5 \end{vmatrix} $$

Expand the determinant:

$$ \vec{v}\times\vec{B} = \hat{i}\bigl((-2)(-5) - (3)(3)\bigr) - \hat{j}\bigl(1(-5) - 3(2)\bigr) + \hat{k}\bigl(1\cdot3 - (-2)\cdot2\bigr) $$
$$ = \hat{i}\bigl(10 - 9\bigr) - \hat{j}\bigl(-5 - 6\bigr) + \hat{k}\bigl(3 + 4\bigr) $$
$$ = 1\,\hat{i} + 11\,\hat{j} + 7\,\hat{k} $$

Magnitude of the cross product:
$$ \lvert\vec{v}\times\vec{B}\rvert = \sqrt{1^{2}+11^{2}+7^{2}} = \sqrt{1+121+49} = \sqrt{171} $$

Therefore, the magnitude of the magnetic force is
$$ F = q\,\lvert\vec{v}\times\vec{B}\rvert = \bigl(1\times10^{-6}\bigr)\sqrt{171}\;\text{N} = \sqrt{171}\times10^{-6}\;\text{N} $$

Comparing with the required form $$\sqrt{\alpha}\times10^{-6}\,\text{N}$$, we have $$\alpha = 171$$.

Hence, the value of $$\alpha$$ is 171.

Get AI Help

Video Solution

video

Create a FREE account and get:

  • Free JEE Mains Previous Papers PDF
  • Take JEE Mains paper tests

Free JEE Topicwise Questions

JEE Atomic StructureJEE Applications of DerivativesJEE Complex NumbersJEE Fluid MechanicsJEE Alcohols, Phenols & EthersJEE Basic Principles of Organic ChemistryJEE Trigonometric FunctionsJEE Three Dimensional GeometryJEE Electromagnetic WavesJEE Redox ReactionsJEE SolutionsJEE Laws of ThermodynamicsJEE Ray OpticsJEE Organic Compounds with HalogensJEE Chemical ThermodynamicsJEE Permutations & CombinationsJEE DeterminantsJEE EMF & Circuit AnalysisJEE Aldehydes & KetonesJEE Atoms & NucleiJEE Dual Nature of Matter & RadiationJEE Electric Charges & FieldsJEE Number SystemJEE Units & MeasurementsJEE Simple Harmonic MotionJEE ElasticityJEE Alternating CurrentsJEE Practical Organic ChemistryJEE Electromagnetic InductionJEE Rotational MotionJEE Hydrocarbons - AlkynesJEE CirclesJEE Kinematics - 1D MotionJEE Purification & CharacterisationJEE Nitrogen-Containing CompoundsJEE Magnetism & Magnetic MaterialsJEE Basic Concepts in ChemistryJEE Laboratory Experiments - XIJEE Periodic Table & PeriodicityJEE Coordination CompoundsJEE Inverse Trigonometric FunctionsJEE Kinetic Theory of GasesJEE Carboxylic AcidsJEE Hydrocarbons - AlkanesJEE d and f-Block ElementsJEE StatisticsJEE LimitsJEE Laws of MotionJEE Electronic DevicesJEE Continuity & DifferentiabilityJEE Sets, Relations & FunctionsJEE Work, Energy & PowerJEE Straight LinesJEE Surface TensionJEE Vector AlgebraJEE ElectrochemistryJEE Kinematics - 2D MotionJEE Chemical KineticsJEE Magnetic Effects of CurrentJEE Binomial TheoremJEE Definite IntegrationJEE ProbabilityJEE Sequences & SeriesJEE Hydrocarbons - AromaticJEE Chemical Bonding & Molecular StructureJEE Hydrocarbons - AlkenesJEE Quadratic EquationsJEE DifferentiationJEE GravitationJEE JEE 2D GeometryJEE p-Block Elements (Groups 13-18)JEE Wave OpticsJEE BiomoleculesJEE Heat TransferJEE Current & ResistanceJEE MatricesJEE Differential EquationsJEE EquilibriumJEE WavesJEE Indefinite IntegrationJEE Electric Potential & CapacitanceJEE Conic Sections
Ask AI