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Class 6 Science NCERT Part 6: Chapter 11-12 Presented by Dr. Roman Saini
About me MBBS, AIIMS 706-1334 EST Cleared CSE-2013 Loves playing Guitar, Movie Buff * Course Fee : Contribute Follow me on Unacademy https://unacademy.in/user/RomanSaini
Chapter 11: Light, shadows and reflections , Luminous objects: objects emitting their own light. Ex: Stars like sun Light will fall on an object first and then it will travel to our eyes, only then it will be visible (unless it is luminescent) On basis of visibility, passage of light, objects are: Transparent (absolutely clearly), opaque (nothing at all) and translucent (not very clearly, somewhat in middle) screen in the background, gives an idea about shape of object, may mislead also Light travels in a straight line
Pinhole camera: A light proof box, without a lens, with a single small aperture (pinhole). Light passes through this single point and produces an inverted image on opposite wall of the box. Natural pinhole: Small spaces in between tree leaves * Reflection: Change in direction of light (technically wave front) between 2 different media and its return in media of origin , Mirrors, lakes, ponds etc. are reflecting surfaces Periscope: Instrument which make observation of an object possible, which is otherwise not in direct line of sight of observer's current position.
1 C1 2 C3/b C3/02
Chapter 12: Electricity and Circuits Electricity: Physical phenomenon-presence and flow of electric charge. Leads to lightning, static electricity, electromagnetic induction and electrical current. Carelessness: Can cause injury, including death (Our body is a conductor) Electric cell: Metal cap (+) metal disc (), chemicals stores electricity, once started it goes on depleting (even when not in use). Alessandro Volta Joining these 2 ends without a switch or device, leads to consumption of chemicals very fast. s Electric bulb: Thin wire in bulb that gives light - filament (W, Tungsten, break leads to bulb being fused). Bulb also has 2 terminals (base+ metal tip of base, fix so they don't touch each other), Thomas Alva Edison
Filament of the bulb is connected to its 2 terminus. Bulb glows when electric current passes through it Material that allow current to pass through them : Conductor (metals like copper, silver, iron) Switches, electrical plugs and sockets Doesn't allow, high resistivity : Insulator (air, plastic, rubber, wood, ceramic, polyethylene, paper, mineral oil), touchable or exposed parts are covered by insulators- electrical wires plug tops, switches switch: simple device used to break/ complete electric circuit Closed electric circuit Electric current passes from one terminal to another, direction of current is form + terminal to terminal Why rubber gloves are used by electrician, screwdrivers, testers also have plastic covering: (rubber is bad conductor)