Physics in Depth

Electric Charges & Electrostatics - Class 11 Physics Electric Charges Electrostatics , the earliest discovered branch of electricity, involves electric charges, the forces between them, and their behavior in materials. Just as masses are responsible for gravitational forces, electric charges are the fundamental property responsible for electrical forces. Matter is made up of atoms. Inside every atom, positive and negative charges are held together by the enormous attraction of the electrical force. Protons carry a positive charge, while electrons carry a negative charge. Protons are bound tightly inside the nucleus of an atom and are not mobile, unlike the tinier electrons ( electrons do all sorts of useful things! ). Bohr model of an atom (Class 11) Concentric circular orbits around a central nucleus. Three shells labelled K, L, M contain 2, 8, and 8 electrons respectively. Protons are shown as red circles and neutrons as grey circles in...

Pullinger's Apparatus: Coefficient of Linear Expansion Pullinger's Apparatus Figure: Pullinger's Apparatus Pullinger's apparatus is a laboratory instrument used to determine the coefficient of linear expansion of a metal rod. Description A long cylindrical metal steam jacket (or hollow tube) encloses the experimental metal rod AB . The thermometer T is inserted into the side of the jacket to measure the temperature of the system (steam/rod environment). A spherometer is placed at the top on a stable base plate to precisely measure the tiny change in the rod's length. A galvanometer ( G ) is connected to a battery through the key ( K ) to signal the accurate reading position when an electrical contact is established. Working Principle The initial length of the rod \((L_1)\) is measured at room temperature \((\theta_1)\). With the lowering of the central leg of the sphe...

NEB Grade XII 2079 (2022) Physics Question Solution New Course Group 'A' Rewrite the correct options of each question in your answer sheet. If L represents momentum, I represents moment of inertia, then \(\frac{L^2}{2I}\) represents Rotational kinetic energy Torque Power Potential energy Solution: Option (a) Explanation: Since, the rotational kinetic energy is commonly expressed as, \[\text{K.E.}=\frac{1}{2}mv^2\] Also, \[L=I\omega\] Then, \[\begin{align*} \text{K.E.}&=\frac{1}{2} I \times \frac{L^2}{I^2}\\ &=\frac{L^2}{2I}\\ \end{align*}\] Starting from mean position, a particle in simple harmonic motion takes time \(T_1\) and \(T_2\) to cover first half and next half displacement in moving from mean to extreme position, then ...