Physics in Depth

Action at Points | Class 11 NEB Physics | Physics in Depth Action at Points: Action at points refers to the phenomenon where a charged pointed end of a conductor ionizes the surrounding air causing a continuous leakage of charge from that point. Mechanism: For any charged conductor, the electric charge distributes itself on the outer surface. For a pointed end, the surface charge density (\(\sigma\), charge per unit area) is inversely proportional to the radius of curvature (\(r\)) of that surface:\[\sigma \propto \frac{1}{r}\] The electric field \(E\) is proportional to \(\sigma\). So, the two case may arise: Case I: The electric field if immensely greater may ionize the air molecules directly stripping the electrons from it (air molecules then becomes positively charged). Case II: The higher electric field intensity due to the pointed end may ...

Electric Charges & Electrostatics — Class 11 Physics Electric Charges Class 11 Physics  ·  Electrostatics Contents Introduction Conservation of Charge Quantization of Charge Methods of Charging Magnitude of One Coulomb Coulomb's Law Conceptual & Numerical Challenges Introduction 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 tig...

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...

Model Question Solution — Physics Model Question Solution Physics  ·  NEB Examination Preparation Contents Group A — MCQs Group B — Short & Long Answer Surface Tension Terminal Velocity Moment of Inertia Bernoulli's Theorem Sound & Harmonics Thermodynamics Magnetic Flux Density EM Induction Photoelectric Effect Bohr's Model Simple Harmonic Motion LRC Circuit Potentiometer Charge Quantization Radioactivity GROUP A Multiple Choice Questions 1 Which of the following is a correct formula for calculating radius of gyration of a rotating object? Solution Option (a)   \(k^2=\dfrac{I}{m}\) Explanation \[I=MK^2\] \[\therefore K^2=\frac{I}{M}\] 2 A h...