Moving Charges and Magnetism appeared 3 times across 1 year — 6.7% of Physics.
This question is from Magnetic Field on the Axis of a Circular Current Loop.
A 100$100$-turn closely wound circular coil of radius 5 ~cm$5 \mathrm{~cm}$ has a magnetic field 3.14 × 10⁻³ ~T$3.14 \times 10^{-3} \mathrm{~T}$ at its centre. The current flowing through the coil, and the magnitude of the magnetic moment of the coil are, respectively -
(Take μ₀ = 4π × 10⁻⁷ ~Tm/A$\mu_0 = 4\pi \times 10^{-7} \mathrm{~Tm/A}$)
Keywords:#100-turn closely wound circular coil#NEET 2026 Code 12 Q1#Moving Charges and Magnetism NEET 2026#Magnetic Field on the Axis of a Circular Current Loop NEET 2026
More Moving Charges and Magnetism Previous-Year Questions
Q8neet_2026_03_may_morningAmpere's Circuital Law
The figure given below shows a long straight solid wire of circular cross-section of radius 'a' carrying steady current I$I$. The current I$I$ is uniformly distributed across its cross-section. The plot which correctly represents the variation of magnetic field (B$B$) with distance (r$r$) from the axis of the conductor in the region is
Cross section showing radius a for a steady current wire.
For a long straight solid wire carrying a steady current that is uniformly distributed across its cross-section:
Inside the wire (r < a$r < a$), the magnetic field is directly proportional to the distance from the axis (B ∝ r$B \propto r$). This represents a straight line passing through the origin.
Outside the wire (r > a$r > a$), the magnetic field is inversely proportional to the distance from the axis (B ∝ (1)/(r)$B \propto \frac{1}{r}$). This represents a rectangular hyperbola.
Step 1: Graph Identification
The correct graph must show a linear increase starting from the origin up to r=a$r=a$, followed by a smooth 1/r$1/r$ hyperbolic curve decaying towards zero for r>a$r>a$. The plot matching this criteria is option 1.
Pattern Recognition
Solid cylinder uniform current: Inside B ∝ r$B \propto r$ (linear), outside B ∝ 1/r$B \propto 1/r$ (curve). Hollow cylinder: Inside B = 0$B = 0$, outside B ∝ 1/r$B \propto 1/r$.
Chapter Mix
Class 12 Physics: Moving Charges and Magnetism
Q12neet_2026_03_may_morningConversion of Galvanometer to Ammeter
A galvanometer of resistance 100Ω$100\Omega$ gives full scale deflection for a current of 1 ~mA$1 \mathrm{~mA}$. It is converted into an ammeter of range 0--10 ~A$0\text{--}10 \mathrm{~A}$. The shunt required is:
Given:
Galvanometer resistance RG = 100 Ω$R_G = 100 \Omega$
Full scale deflection current IG = 1 ~mA = 0.001 ~A$I_G = 1 \mathrm{~mA} = 0.001 \mathrm{~A}$
Target range current I = 10 ~A$I = 10 \mathrm{~A}$
The shunt resistance RS$R_S$ is connected in parallel with the galvanometer. Since they are in parallel, the potential difference across them is equal.
VS = VG$V_S = V_G$
(I - IG)RS = IG RG$$(I - I_G)R_S = I_G R_G$$
Because IG (0.001 ~A)$I_G (0.001 \mathrm{~A})$ is very small compared to I (10 ~A)$I (10 \mathrm{~A})$, we can approximate (I - IG) ≈ I = 10 ~A$(I - I_G) \approx I = 10 \mathrm{~A}$.
Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.
