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Moving Charges and Magnetism Set-2 MCQ Online Practice Test | Class 12 | Quiz Tweek

Moving Charges and Magnetism Set-2

Practice Important MCQs for Moving Charges and Magnetism — Physics, Class 12.

Moving Charges and Magnetism is a core Class 12 Physics chapter that connects electricity with magnetism through the ideas of magnetic force on moving charges, magnetic fields due to currents, and motion of charged particles in magnetic fields. These concepts form the basis of many standard CBSE board questions and are repeatedly used in numericals involving Lorentz force, Biot–Savart law, Ampere’s circuital law, and force between current-carrying conductors.

This chapter is also crucial for understanding real devices and experiments such as cyclotrons, moving-coil galvanometers, current balance definition of ampere, and magnetic field mapping for common current geometries (wire, loop, solenoid, toroid). Mastery of key formulae, vector directions (right-hand rules), and typical approximations helps in scoring well in both CBSE board-level problems and JEE/NEET-aligned MCQs.

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Q1. A charge $q$ moves with velocity $\vec v$ in a uniform magnetic field $\vec B$ . The magnetic force on it is maximum when the angle between $\vec v$ and $\vec B$ is:

(A)

$0^\circ$

(B)

$30^\circ$

(C)

$60^\circ$

(D)

$90^\circ$

Q2. A proton enters a uniform magnetic field $\vec B$ with velocity $\vec v$ perpendicular to $\vec B$ . The path followed is:

(A)

Straight line

(B)

Parabola

(C)

Circle

(D)

Helix

Q3. The radius of circular path of a charged particle (charge $q$ , mass $m$ ) moving with speed $v$ perpendicular to a uniform magnetic field $B$ is:

(A)

$r=\dfrac{qB}{mv}$

(B)

$r=\dfrac{mv}{qB}$

(C)

$r=\dfrac{mB}{qv}$

(D)

$r=\dfrac{qv}{mB}$

Q4. The time period of a charged particle in uniform circular motion in a magnetic field $B$ (with velocity perpendicular to $B$ ) is:

(A)

$T=\dfrac{2\pi m}{qB}$

(B)

$T=\dfrac{2\pi q}{mB}$

(C)

$T=\dfrac{2\pi mv}{qB}$

(D)

$T=\dfrac{2\pi mB}{qv}$

Q5. A charged particle enters a uniform magnetic field with velocity having components $v_\perp$ and $v_\parallel$ relative to $\vec B$ . Its trajectory is:

(A)

Straight line along $\vec B$

(B)

Circle

(C)

Helix

(D)

Parabola

Q6. The pitch of the helical path of a charged particle moving in a uniform magnetic field is:

(A)

$\dfrac{2\pi m v_\perp}{qB}$

(B)

$\dfrac{2\pi m v_\parallel}{qB}$

(C)

$\dfrac{qB v_\parallel}{2\pi m}$

(D)

$\dfrac{2\pi m}{qB}$

Q7. A charged particle moves in a uniform magnetic field. The work done by magnetic force on the particle is:

(A)

Maximum

(B)

Minimum but non-zero

(C)

Zero

(D)

Depends on speed

Q8. SI unit of magnetic field $B$ is:

(A)

Weber

(B)

Tesla

(C)

Henry

(D)

Coulomb

Q9. The magnetic field at a distance $r$ from a long straight wire carrying current $I$ in free space is:

(A)

$B=\dfrac{\mu_0 I}{2\pi r}$

(B)

$B=\dfrac{\mu_0 I}{4\pi r}$

(C)

$B=\dfrac{\mu_0 I r}{2\pi}$

(D)

$B=\dfrac{\mu_0 I}{2\pi r^2}$

Q10. Two long parallel wires carry currents $I_1$ and $I_2$ in the same direction. The force between them is:

(A)

Repulsive

(B)

Attractive

(C)

Zero

(D)

Alternating between attractive and repulsive

Q11. The force per unit length between two long parallel wires separated by distance $d$ , carrying currents $I_1$ and $I_2$ , is:

(A)

$\dfrac{\mu_0 I_1 I_2}{2\pi d}$

(B)

$\dfrac{\mu_0 I_1 I_2}{4\pi d}$

(C)

$\dfrac{\mu_0 I_1 I_2 d}{2\pi}$

(D)

$\dfrac{2\pi d}{\mu_0 I_1 I_2}$

Q12. A current-carrying conductor of length $L$ carrying current $I$ is placed in a uniform magnetic field $\vec B$ . The force on it is maximum when the angle between conductor (current direction) and $\vec B$ is:

(A)

$0^\circ$

(B)

$30^\circ$

(C)

$60^\circ$

(D)

$90^\circ$

Q13. A circular loop of radius $R$ carrying current $I$ produces magnetic field at its center:

(A)

$B=\dfrac{\mu_0 I}{2\pi R}$

(B)

$B=\dfrac{\mu_0 I}{4\pi R}$

(C)

$B=\dfrac{\mu_0 I}{2R}$

(D)

$B=\dfrac{\mu_0 I}{R}$

Q14. For a circular coil of $N$ turns, radius $R$ , carrying current $I$ , the magnetic field at the center is:

(A)

$B=\dfrac{\mu_0 NI}{2R}$

(B)

$B=\dfrac{\mu_0 I}{2NR}$

(C)

$B=\dfrac{\mu_0 NI}{R}$

(D)

$B=\dfrac{\mu_0 I}{R}$

Q15. Magnetic field inside a long solenoid having $n$ turns per unit length carrying current $I$ is:

(A)

$B=\dfrac{\mu_0 I}{2\pi r}$

(B)

$B=\mu_0 n I$

(C)

$B=\dfrac{\mu_0 n I}{2}$

(D)

$B=\dfrac{\mu_0 n I}{r}$

...and 15 more challenging questions available in the interactive simulator.

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