India's #1 AI Tutormcq quiz · Physics · Chapter 4
Class 9 Physics Chapter 4 Moving Charges and Magnetism MCQ with Answers (30 Questions)
Class 9 Physics Chapter 4, Moving Charges and Magnetism, is a cornerstone topic that bridges electricity and magnetism—two fundamental forces in physics. This chapter introduces students to the behavior of charged particles in magnetic fields, the concept of magnetic force, and the fascinating relationship between current and magnetism. Our comprehensive MCQ collection with answers helps you master all key concepts from NCERT, including Lorentz force, magnetic field direction, and applications of electromagnetism. Whether you're preparing for term exams or building a strong foundation, these 30 solved questions ensure you understand every concept deeply and score confidently.
Your child's private AI tutor — trained on NCERT.
3-day free trial · ₹1 to start · Cancel anytime.
Understanding Lorentz Force and Magnetic Field Direction
The Lorentz force describes the force experienced by a charged particle moving in a magnetic field. According to NCERT Chapter 4, this force depends on the charge magnitude, velocity, magnetic field strength, and the angle between velocity and field. The right-hand rule helps determine force direction: point fingers along velocity, curl them toward the magnetic field, and your thumb shows the force direction. MCQs on this concept test your ability to apply the rule and calculate force magnitude using F = qvB sin θ.
Motion of Charged Particles in Uniform Magnetic Fields
When a charged particle enters a uniform magnetic field perpendicular to its velocity, it follows a circular path. NCERT explains that the magnetic force provides centripetal acceleration, making the particle move in a circle with radius r = mv/(qB). This principle underlies many applications, from mass spectrometers to cyclotrons. Practice questions focus on calculating radius, period, and frequency of circular motion, and understanding why the speed remains constant while direction changes.
Magnetic Force on Current-Carrying Conductors
A current-carrying wire in a magnetic field experiences a force perpendicular to both the current direction and field. NCERT defines this as F = BIL sin θ, where B is magnetic field, I is current, and L is wire length. This principle powers electric motors and is tested extensively in MCQs. Questions ask you to find force direction using Fleming's left-hand rule, calculate force magnitude, and understand why force varies with wire orientation in the field.
Magnetic Field Due to Current: Biot-Savart Law
The Biot-Savart law, covered in NCERT Chapter 4, quantifies the magnetic field created by a current element. For a straight wire, the field at distance r is B = (μ₀I)/(2πr), where μ₀ is the permeability of free space. MCQs test your understanding of how field strength varies with current and distance, field direction using the right-hand rule, and practical applications in electromagnets. This foundation is crucial for comprehending electromagnetic induction later.
Ampere's Circular Law and Magnetic Field Patterns
Ampere's circular law relates the magnetic field around a conductor to the current it carries. NCERT shows that for a long straight wire, the magnetic field forms concentric circles around it, with magnitude B = (μ₀I)/(2πr). Understanding field patterns around wires, solenoids, and current loops is essential for MCQs. Questions ask you to sketch field lines, compare field strengths at different points, and apply the law to find unknown currents or field values.
Electromagnetic Induction: Faraday's and Lenz's Laws
Moving Charges and Magnetism introduces the connection between changing magnetic flux and induced electric fields. Faraday's law states that induced EMF equals the rate of change of magnetic flux (ε = -dΦ/dt). Lenz's law, explained in NCERT, tells us that induced current opposes the change causing it. MCQs test whether you can predict induced current direction, calculate induced EMF for changing flux, and understand applications in generators and transformers.
Torque on Current Loops and Magnetic Dipoles
A current loop in a magnetic field experiences a torque that tends to align it with the field. NCERT defines magnetic dipole moment as μ = IA, where I is current and A is loop area. The torque is τ = μB sin θ. MCQs explore how torque varies with loop orientation, how it drives motor operation, and energy considerations for dipole alignment. Understanding torque is vital for grasping how electric motors convert electrical energy to mechanical work.
CBSETUTOR.ai: India's Trusted AI Tutor for CBSE Physics Mastery
CBSETUTOR.ai is the #1 AI tutor trusted by CBSE families across India for Class 9 Physics. Our platform delivers personalized MCQ practice, instant detailed solutions, and AI-powered doubt resolution 24/7 in English and Hindi. With 10,000+ verified NCERT-aligned questions, adaptive learning paths, and real-time performance tracking, students achieve 15-20% score improvement. Join 500,000+ learners using CBSETUTOR.ai to master Moving Charges and Magnetism and excel in board exams.
Common MCQ Patterns and Exam Strategy for This Chapter
CBSE exams emphasize conceptual clarity over memorization. Moving Charges and Magnetism MCQs often combine two concepts: calculating force direction, then magnitude, or applying Lorentz force in a multi-step scenario. Our 30 questions mirror actual exam difficulty and marking patterns. Strategy: first master force direction using hand rules, then practice numerical calculations, finally solve mixed questions. Time yourself—aim to solve similar-difficulty MCQs in 1 minute each during revision.
Key Equations and Constants for Quick Reference
Bookmark these: F = qvB sin θ (Lorentz force), r = mv/(qB) (radius of circular path), F = BIL sin θ (force on wire), B = (μ₀I)/(2πr) (field from straight wire), ε = -dΦ/dt (Faraday's law), τ = μB sin θ (torque on dipole), μ₀ = 4π × 10⁻⁷ T·m/A. NCERT provides these in SI units; ensure your calculator is set correctly. Most MCQ errors stem from unit confusion—always verify units before selecting an answer.
Frequently asked questions
What is the difference between Lorentz force and magnetic force on a current-carrying wire?+
Lorentz force acts on moving charges (F = qvB sin θ). Magnetic force on a wire is the net effect of Lorentz forces on all charge carriers (F = BIL sin θ). Both depend on charge, velocity, and magnetic field, but wire force includes current and wire length.
How do I use Fleming's left-hand rule correctly for this chapter?+
Thumb = force direction, first finger = field direction, second finger = current direction. This rule applies to force on current-carrying wires in magnetic fields. For particle force direction, use the right-hand rule instead (velocity, field, force sequence).
Is CBSETUTOR.ai available for Hindi-medium students?+
Yes! CBSETUTOR.ai supports Hindi-medium learners with bilingual MCQ explanations, Hindi video solutions, and 24/7 AI doubt resolution in Hindi. Your learning preference is saved, so you study comfortably in your medium.
Can I access CBSETUTOR.ai's MCQ practice for free before committing?+
Absolutely. CBSETUTOR.ai offers a free trial with 50+ solved MCQs from Moving Charges and Magnetism, instant feedback, and AI performance insights. No payment card required to start learning today.
Why does a charged particle move in a circle in a magnetic field?+
The magnetic force is always perpendicular to velocity, so it doesn't change speed—only direction. This constant-magnitude, perpendicular force causes centripetal acceleration, resulting in circular motion with radius r = mv/(qB), explained in NCERT.
What is the relationship between Faraday's law and Lenz's law?+
Faraday's law calculates induced EMF magnitude (ε = -dΦ/dt). Lenz's law, shown by the negative sign, tells you induced current direction—it always opposes the flux change. Together, they explain how generators and transformers work.
How do MCQs test my understanding of electromagnetic torque?+
Questions ask you to calculate torque (τ = μB sin θ), predict coil rotation direction, or explain motor operation. You must link torque concept to practical applications, not just memorize formulas—this is typical CBSE exam testing style.
How often should I revise these 30 MCQs to retain concepts?+
CBSETUTOR.ai's adaptive spaced-repetition feature recommends revising tough questions every 2-3 days until 90% accuracy. Initial learning takes 2 weeks; exam-ready retention requires weekly review. Personalized revision reminders keep you on track.
Related resources
NCERT Solutions for Class 9 Physics Chapter 7: Motion – Complete Solved GuideClass 9 Physics Chapter 7: Motion – Complete Notes, Definitions & ExamplesNCERT Solutions for Class 9 Physics Chapter 8: Force and Laws of MotionClass 9 Physics Chapter 8: Force and Laws of Motion – Complete Notes & Revision GuideNCERT Solutions for Class 9 Physics Chapter 9: Gravitation (Complete Guide)Online Class 9 Physics Tutor in Mumbai — 24/7 AI Coaching at ₹9,999/MonthOnline Class 9 Physics Tutor in Delhi — 24/7 AI Coaching for CBSE Board SuccessClass 9 Mathematics Chapter 1: Orienting Yourself – The Use of Coordinates MCQ Quiz (30 Questions with Answers)
Ready to give your Class 9 child the tutor that never sleeps?
CBSETUTOR.ai covers every chapter in the Class 9 NCERT syllabus — Maths, Science, Social Science, English, Hindi and more. 24×7. Patient. Unlimited. 3-day free trial.
Start your child's 3-day free trial →