Transcript Slide 1
Electrostatics Effects in Everyday Life Electric & magnetic effects in every day life Electric phenomena may produce magnetic effects and magnetic phenomena may produce electric effects Electromagnetism Study of the effects of electric charges at rest or in motion (Electromagnetic effects ) Electromagnetic effects can be explained by MWE Electromagnetic interaction Only between those bodies or particles which have a property called charge Types of interactions (strong, weak, tensile, adhesive) Definition of charge Brief History of Electromagnetic effects Brief History Brief History 900 BC – Greek shepherd ‘Magnus’ (a story about Asia Minor-the region was called as Magnesia) The word magnet has come from Greek word magnitis lithos meaning magnesian stone- later on called as loadstone - Loadstone effect 600 BC – Greek philosopher Thales (Discovered another material called amber (from Greek word elektron) which when rubbed with wool will attract cat fur) – Amber effect 370 BC – Plato (both amber effect and loadstone effect are related with each other and of the same type) 120 AD – Plutarc (Load stone emits exhaltations which pushes air) 1100 AD – Chinese (magnetic needle pointing northsouth) 1550 AD – Carden (amber and load stone do not attract in the same way) 1600 AD – Gilbert (Introduced science of magnetism by experimentation) Introduction of other substances that would attract when rubbed e.g., glass, sulphur, wax crystals etc) 1752 AD – Benjamin Franklin (Kite flying in thunder storm) 1780 AD – Galvani (idea of moving charges) 1784 AD – Coulomb (measured the electric force) 1792 AD– Volta introduced battery (copper & zinc separated by material soaked in Brine solutioninvented battery) 19th Century – Biot, Savart, Ampere, Oersted, Faraday (relationship between electricity & magnetism) 1864 AD – Maxwell’s contribution & later Hertz experimental evidence Charges residing on objects explain electrostatic effects and dynamics of charges explain magnetic effects Engineering Applications – Laser printer, photocopying, Electrostatic paint spraying Charge-the basic entity of Electromagnetism Properties of charge Charge is quantized Charge is conserved Existence of two types of charges Plastic rod rubbed with wool----- -ve charge Glass rod rubbed with silk -------- +ve charge COULOMB’S LAW Electrostatic force Qualitative analysis – Shifting of electrons is responsible for electrostatics force The net charge of a body is represented by ‘q’ Scalar quantity Units 1 C= ------- electrons Quantitative analysis (measurement of electrostatic force) In order to determine the nature of electrostatic force, the magnitude and direction of electrostatic force is required to be measured Experimental arrangements – Torsion balance Outcomes of the experiment Mathematical expression of Coulomb force between two point charges Constant ‘K’ Properties of Coulomb force Principle of linear superposition Significance of Coulomb’s law Vector form of Coulomb’s Law Example All Examples of Chapter 25 (H-R-K) Problems (25.1 – 25.13) APPLICATIONS Coulomb force by continuous charge distribution In many applications electric forces are exerted by charged objects in the form of rods, plates or solids Then how the Coulomb’s law can be applied? Procedure to determine Coulomb force Imagine the division of charge distribution into large number of small charge elements Consider any one of the charge element Express the charge element in terms of charge density & size of charge element Treating charge element as point charge and determine the force element Determination of direction of force element Calculation of total force Applications Line of charge Ring of charge Disc of charge