Ampere's Circuital Law states that around any CLOSED loop, the line integral of $\vec{B}\cdot d\vec{l}$ equals

1. NCERT §4.5 states Ampere's Law: $\oint\vec{B}\cdot d\vec{l} = \mu_0\,I_\text{enc}$. 2. The LEFT side is the line integral of $\vec{B}$ around any CLOSED loop (Amperian loop). 3. The RIGHT side is $\mu_0$ times the TOTAL CURRENT passing through any surface bounded by the loop. 4. Sign convention: use the right-hand rule on the loop's orientation — current parallel to thumb is positive. 5. Same as Gauss's law in spirit: useful when SYMMETRY (cylindrical, planar, toroidal) lets you pull $B$ outside the integral. 6. Option A is Gauss's law for electricity. Options C and D have wrong functional forms. _Source: NCERT Class 12 Physics Part 1, Ch 4, §4.5 (Ampere's Circuital Law, Eq. 4.20), p. 14–15._