Magnetic field around straight current-carrying wire is: MCQ with Answer and Explanation

Magnetic field around straight current-carrying wire is:
A. Radial
B. Uniform
C. Circular concentric
D. Parallel to wire
Answer: Option C
Solution (By JKExamLibrary)
Biot-Savart law: field forms concentric circles around wire, direction by right-hand thumb rule. Magnitude B = μ₀I/(2πr), decreasing with distance. Memory tip: 'Right-hand rule: thumb = current, fingers = field circles'. Fundamental magnetism concept frequently tested in competitive exams.

This question belongs to: Science Physics

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Question #1 Report Error
A particle moves with velocity v = 3t² + 2t. Its acceleration at t = 2 s is:
A. 16 m/s²
B. 14 m/s²
C. 8 m/s²
D. 10 m/s²

Correct Answer: Option B


Explanation:
Acceleration a = dv/dt = d(3t² + 2t)/dt = 6t + 2. At t = 2 s: a = 6(2) + 2 = 14 m/s². Differentiation of velocity gives instantaneous acceleration. Memory tip: a = dv/dt; for polynomial v(t), differentiate term by term. Tests calculus application in kinematics, common in advanced competitive exam questions.

This question belongs to: Science Physics
Question #2 Report Error
The unit of power, watt, is equivalent to
A. J/s
B. J s
C. N/s
D. N m

Correct Answer: Option A


Explanation:
Watt = joule per second.

This question belongs to: Science Physics
Question #3 Report Error
Assertion (A): Gamma rays are fundamentally un-deflected by electric and magnetic fields. Reason (R): Gamma rays carry no electrical charge.
A. A is true but R is false.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is false but R is true.
D. Both A and R are true and R is the correct explanation of A.

Correct Answer: Option D


Explanation:
Electric fields deflect charged particles via Coulomb forces (F=qE), and magnetic fields deflect moving charged particles via Lorentz forces (F=qvB). Gamma rays are purely high-energy electromagnetic photons. Because they lack any electrical charge (q=0), both electric and magnetic forces on them are exactly zero. Therefore, they pass through fields completely un-deflected. R explains A perfectly.

This question belongs to: Science Physics