Wire stretched to double length (volume constant). New resistance: MCQ with Answer and Explanation

Explanation:
According to Ampere's force law, parallel wires carrying currents in the SAME direction create magnetic fields that attract each other. Conversely, parallel wires carrying currents in OPPOSITE directions create magnetic fields that push against each other, causing the wires to repel. Exam tip: 'Same' Attracts, 'Opposite' Repels (reverse of charges!).

Explanation:
For a concave mirror, when an object is placed exactly at the center of curvature (C), the image is also formed at C. The image is real (can be captured on a screen), inverted (upside down), and exactly the same size as the object. Magnification in this specific case is exactly -1.

Explanation:
Optical fibers consist of a central core surrounded by a cladding with a slightly lower refractive index. When a light beam enters the core at an angle greater than the critical angle, it undergoes multiple successive total internal reflections against the core-cladding boundary. This allows the light to travel over vast distances with virtually no loss of energy, making it ideal for telecommunications.