The device used to convert DC to AC is MCQ with Answer and Explanation

Explanation:
Vernier caliper is ideal for measuring internal diameters of narrow tubes due to its internal jaws designed for such measurements. Screw gauge measures external dimensions like wire diameter. Meter scale and measuring tape lack the precision (least count ~1 mm) needed for narrow tubes. Vernier calipers typically have least count 0.01 mm or 0.02 mm. Practical tip: Always use internal jaws for internal measurements, external jaws for outer dimensions. This application-based question tests knowledge of instrument selection in experimental physics, commonly featured in practical examination sections.

Explanation:
By definition, the electric potential difference between two points in an electric field is the amount of external work required to move a unit positive charge (1 Coulomb) slowly and without acceleration from one point to the other against the electrostatic force. The SI unit of potential difference is the Volt (Joules/Coulomb).

Explanation:
Bohr model: r_n = n²a₀ ⇒ r ∝ n². Higher n = larger orbit. Memory tip: 'Bohr: r ∝ n²; E ∝ -1/n²'. Atomic physics relation frequently tested in competitive exams.