logging in or signing up CP-1 ELECTROSTATICS For XII PHYSICS mahenphy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 603 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: March 10, 2011 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: zaine (3 month(s) ago) how to download this amazing ppt now Saving..... Post Reply Close Saving..... Edit Comment Close By: zaine (3 month(s) ago) plz i wanna this ppt right now....this is really good one i wanna this right now plz Saving..... Post Reply Close Saving..... 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Email-msr.phy20@gmail.com 1 Mahendra singh PGT (PHY)Electrostatics: Electrostatics “A branch of physics which deals with study of interaction between stationary charges is known as Electrostatics” 2 Mahendra singh PGT (PHY)What is electric charge: What is electric charge The ancient Greeks discovered as early as 600 B.C. that after they rubbed amber with wool, the amber could attract other objects. Today we say that the amber has acquired a net electric charge, or has become charged. The word "electric" is derived from the Greek word elektron , meaning amber. 3 Mahendra singh PGT (PHY)Electric charges: Electric charges It is a fundamental property of matter which already exists in them and appears due to transfer of electrons of one to another. 4 Mahendra singh PGT (PHY)Types of electric charges: Types of electric charges Benjamin Franklin (1706-1790) suggested that two kinds of charge negative and positive. Two positive charges or two negative charges repel each other. A positive charge and a negative charge attract each other. 5 Mahendra singh PGT (PHY)Some examples of electric charges related to day to day life: Some examples of electric charges related to day to day life 1. Lighting in sky during thunderstorm. 2. Seeing a spark or hearing a crackle when we take off our synthetic clothes or sweater, particularly in dry weather. 3. A sensation of an electric shock either while opening the door of a car or holding the iron bar of a bus after sliding from our seat. 4. Hearing crackles on touching the TV or computer monitor screen. 6 Mahendra singh PGT (PHY)Electrified comb attracts paper strips: Electrified comb attracts paper strips 7 Mahendra singh PGT (PHY)Method of charging: Method of charging There are three method of charging of an object- 1. Charging by friction 2. Charging by induction 3. Charging by conduction 8 Mahendra singh PGT (PHY)1. Charging by friction: 1. Charging by friction When one object rubs with another object, some electrons transfer from one object to another object and two objects become charged due to transfer of charged i.e. one becomes + ve and one becomes – ve but both have equal charge. 9 Mahendra singh PGT (PHY) Example: - objects acquiring two kinds of charges on rubbing (Friction). : Example : - objects acquiring two kinds of charges on rubbing (Friction). S.No . Positive charge Negative charge 1 Glass rod Silk cloth 2 Fur or woolen Ebonite , Amber, Rubber rod 3 Woolen cloth Plastic rod 4 Woolen carpet Rubber shoes 5 Dry hair Comb 10 Mahendra singh PGT (PHY)2. Charging by induction: 2. Charging by induction In charging by induction a charged body imparts some charge of opposite sign to another uncharged body without any actual between them. 11 Mahendra singh PGT (PHY)3. Charging by conduction: 3. Charging by conduction In this method of charging a charged object is charged an uncharged object by direct contact of by means of a conducting wire. i.e. Charging a neutral body by touching it with a charged body. 12 Mahendra singh PGT (PHY)Gold leaf electroscope: Gold leaf electroscope A simple apparatus which is used to detect charge on a body is the gold-leaf Electroscope. Construction: - It consists of a vertical metal rod housed in a box, with two thin gold leaves attached to its bottom end. 13 Mahendra singh PGT (PHY)BASIC PROPERTIES OF ELECTRIC CHARGE: BASIC PROPERTIES OF ELECTRIC CHARGE 1. Charge is conserved: The total charge of the isolated system is always conserved . 2. Quantization of charge: i.e. An object may have a charge ±e, or ± 2e, or ± 3e, etc but not say ± 1.5e. Thus Q= ± ne 3. Additivity of charges 14 Mahendra singh PGT (PHY)CONDUCTORS AND INSULATORS: CONDUCTORS AND INSULATORS Conductor- Those materials which allow electricity to pass through them easily are called conductors . For example- ( i ) silver (ii) copper (iii) aluminum etc. Insulator- Those materials which do not allow electricity to pass through them easily are called insulators. For example- ( i ) wood (ii) plastic (iii) sand etc. 15 Mahendra singh PGT (PHY)Questions: What does q1 + q2 =o signify in electrostatics? [CBSE 2001] What is quantization of charges? If a tiny particle is given a charge; does its mass increase or decrease ? Write any two properties of electric charges? A conductor carries a charge -9.6 x 10-17C. How many free electrons are in the conductor? Questions 16 Mahendra singh PGT (PHY)Electrostatics force: Electrostatics force As similar charges repel each other and opposite charges attracts each other .That force for of repulsion and attraction between two charges particle is called electrostatics force. 17 Mahendra singh PGT (PHY)Coulomb’s Law for Electrostatics: Coulomb’s Law for Electrostatics According to coulomb, “ The electrostatics force between two charge particles is equal to product of their charges and inversely proportional to square of their distance between their centers .” 18 Mahendra singh PGT (PHY)Properties of Electric force: Properties of Electric force It is force of attraction as well as force of repulsion. It is long range force. It is conservative force. It is central force. It obeys inverse square law. It obeys action and reaction law. 19 Mahendra singh PGT (PHY)Dielectric Constant (k): Dielectric Constant (k) K= Electric force in vacuum /Electric force in medium The dielectric constant of given medium is defined as that ration of electric force applied between two electric charges in vacuum to electric force applied between same charges at same distance in given medium. 20 Mahendra singh PGT (PHY)Questions: Questions The force acting between two point charges q1 & q2 kept at some distance apart in air is attractive or repulsive when ( i ) q1q2>0 (ii)q1q2<0 [CBSE 2007] Define dielectric constant of a medium in terms of force between electric charges. [CBSE-1997] The force between two point charges kept at a distance r apart in air is F. If the same charges are kept in water at the same distance, how does the force between them change ? [CBSE1997] 21 Mahendra singh PGT (PHY)Electric Field: Electric Field The space and region around the electric charge in which other charge particles experience force is known as electric field. 22 Mahendra singh PGT (PHY)Electric field intensity: Electric field intensity The electric field intensity at any given point in electric field is defined as force experienced by a unit charge particle at that point. SI Unit – Newton/coulomb It is vector quantity 23 Mahendra singh PGT (PHY)Electric field lines: Electric field lines Electric field lines or lines of force provide a map of the electric field in the space surrounding electric charges. “Electric field lines are defined as the path traced by unit positive charge in electric field, if it is free to do so.” 24 Mahendra singh PGT (PHY)Properties of electric field lines: Properties of electric field lines The lines are hypothetical lines which originate from a positive charge (or infinity) and end at a negative charge (or infinity). No two field lines can cross each other. because if they do so there two directions of electric field at point of intersection which is not possible. The line are perpendicular to the surface of the charge The tangent to an electric field line at a point in space gives the direction of the electric field at that point. 25 Mahendra singh PGT (PHY) Magnetic field lines of positive charge (q>0) : Magnetic field lines of positive charge (q>0) 26 Mahendra singh PGT (PHY) Electric field lines due to negative charge (q<0) : Electric field lines due to negative charge (q<0) 27 Mahendra singh PGT (PHY)Electric field lines due to electric dipole: Electric field lines due to electric dipole 28 Mahendra singh PGT (PHY)Electric field lines due to uniform electric field: Electric field lines due to uniform electric field 29 Mahendra singh PGT (PHY)Questions: Questions The electric field lines never cross each other, why? [ CBSE 1995C] Draw lines of force to represent uniform electric field . [ CBSE 1995,2000,1999,2008] Which physical quantity has unit N/C ? Is it a vector or a scalar quantity ? [ CBSE 2010,2000C] Two point charge q= +3 μ C and q= -3 μ C are located at points A and B , 20 cm apart in vacuum. Find the electric field at the mid point of the line AB joining the two charges .[2003] 30 Mahendra singh PGT (PHY)Electric flux: Electric flux The electric flux through a planar area is defined as the electric field times the component of the area perpendicular to the field. 31 Mahendra singh PGT (PHY)ELECTRIC DIPOLE: ELECTRIC DIPOLE An electric dipole is a pair of equal and opposite point charges q and – q, separated by a distance 2 a . By convention, the direction from – q to q is said to be the direction of the dipole. 32 Mahendra singh PGT (PHY)ELECTRIC DIPOLE MOMENT: ELECTRIC DIPOLE MOMENT The product of either charge and length of electric charge is called electric dipole moment P= q(2l) It is vector quantity It’s unit is Coulomb metre 33 Mahendra singh PGT (PHY)Electric Field due to an Electric Dipole: Electric Field due to an Electric Dipole ( it Axial point- 34 Mahendra singh PGT (PHY)Electric Field due to an Electric Dipole: Electric Field due to an Electric Dipole (ii)At Equatorial point 35 Mahendra singh PGT (PHY)DIPOLE IN A UNIFORM EXTERNAL FIELD: DIPOLE IN A UNIFORM EXTERNAL FIELD Net force- F =(+ qE - qE )=0 No translatory motion Torque- τ = P x E 36 Mahendra singh PGT (PHY)Questions: Questions Define electric dipole moment. Is it a scalar of a vector quantity? [ AI CBSE 2006, 2009] An electric dipole of dipole moment 20 x 10-6 C is enclosed by closed surface. What is the net electric flux coming out of this surface?[CBSE 2005] The distance of field point, on the equatorial plane of a small electric dipole is halved. By what factor does the electric field due to the dipole change ? [CBSE 2004 C] 37 Mahendra singh PGT (PHY)GAUSS’S LAW: GAUSS’S LAW The electric flux Φ E through any closed surface is equal to the net charge inside the surface, Q inside, divided by ε 0 :- 38 Mahendra singh PGT (PHY)Electric Field due to an infinitely long straight uniformly charged wire: Electric Field due to an infinitely long straight uniformly charged wire 39 Mahendra singh PGT (PHY)Electric Field due to a uniformly charged thin spherical shell: Electric Field due to a uniformly charged thin spherical shell Field outside the shell:- Field inside the shell:- 40 Mahendra singh PGT (PHY)Electric Field due to a uniformly charged infinite plane sheet: Electric Field due to a uniformly charged infinite plane sheet 41 Mahendra singh PGT (PHY)Electric field due to charged cylinder: Electric field due to charged cylinder 42 Mahendra singh PGT (PHY)Questions: Questions If the radius of the Gaussian surface enclosing a charge is halved , how does the electric flux through the Gaussian surface change?[2008] State Gauss theorem in electrostatics . Apply this theorem to obtain the expression for the electric field at a point due to an infinitely ling, thin, uniformly charged straight wire of linear charge density λ C/m.{[05,07,08,09] Mahendra singh PGT (PHY) 43Slide 44: 44 Mahendra singh PGT (PHY) You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
CP-1 ELECTROSTATICS For XII PHYSICS mahenphy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 603 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: March 10, 2011 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: zaine (3 month(s) ago) how to download this amazing ppt now Saving..... Post Reply Close Saving..... Edit Comment Close By: zaine (3 month(s) ago) plz i wanna this ppt right now....this is really good one i wanna this right now plz Saving..... Post Reply Close Saving..... Edit Comment Close By: maanrohith (13 month(s) ago) kindly do as soon as possible Saving..... Post Reply Close Saving..... Edit Comment Close By: maanrohith (13 month(s) ago) kindly do as soon as possible Saving..... Post Reply Close Saving..... Edit Comment Close By: maanrohith (13 month(s) ago) dear sir .... ur ppt presentation is the best one i have ever come across ... so kindly make this ppt downloadable plz ....plz....plzz...plz...plz...do the needfull .. regards rohith Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript CP-1 ELECTROSTATICS: CP-1 ELECTROSTATICS XII -PHYSICS MAHEDRA SINGH PGT(PHYSICS) KV,NO.1,AFS,JODHPUR(RAJ.) Email-msr.phy20@gmail.com 1 Mahendra singh PGT (PHY)Electrostatics: Electrostatics “A branch of physics which deals with study of interaction between stationary charges is known as Electrostatics” 2 Mahendra singh PGT (PHY)What is electric charge: What is electric charge The ancient Greeks discovered as early as 600 B.C. that after they rubbed amber with wool, the amber could attract other objects. Today we say that the amber has acquired a net electric charge, or has become charged. The word "electric" is derived from the Greek word elektron , meaning amber. 3 Mahendra singh PGT (PHY)Electric charges: Electric charges It is a fundamental property of matter which already exists in them and appears due to transfer of electrons of one to another. 4 Mahendra singh PGT (PHY)Types of electric charges: Types of electric charges Benjamin Franklin (1706-1790) suggested that two kinds of charge negative and positive. Two positive charges or two negative charges repel each other. A positive charge and a negative charge attract each other. 5 Mahendra singh PGT (PHY)Some examples of electric charges related to day to day life: Some examples of electric charges related to day to day life 1. Lighting in sky during thunderstorm. 2. Seeing a spark or hearing a crackle when we take off our synthetic clothes or sweater, particularly in dry weather. 3. A sensation of an electric shock either while opening the door of a car or holding the iron bar of a bus after sliding from our seat. 4. Hearing crackles on touching the TV or computer monitor screen. 6 Mahendra singh PGT (PHY)Electrified comb attracts paper strips: Electrified comb attracts paper strips 7 Mahendra singh PGT (PHY)Method of charging: Method of charging There are three method of charging of an object- 1. Charging by friction 2. Charging by induction 3. Charging by conduction 8 Mahendra singh PGT (PHY)1. Charging by friction: 1. Charging by friction When one object rubs with another object, some electrons transfer from one object to another object and two objects become charged due to transfer of charged i.e. one becomes + ve and one becomes – ve but both have equal charge. 9 Mahendra singh PGT (PHY) Example: - objects acquiring two kinds of charges on rubbing (Friction). : Example : - objects acquiring two kinds of charges on rubbing (Friction). S.No . Positive charge Negative charge 1 Glass rod Silk cloth 2 Fur or woolen Ebonite , Amber, Rubber rod 3 Woolen cloth Plastic rod 4 Woolen carpet Rubber shoes 5 Dry hair Comb 10 Mahendra singh PGT (PHY)2. Charging by induction: 2. Charging by induction In charging by induction a charged body imparts some charge of opposite sign to another uncharged body without any actual between them. 11 Mahendra singh PGT (PHY)3. Charging by conduction: 3. Charging by conduction In this method of charging a charged object is charged an uncharged object by direct contact of by means of a conducting wire. i.e. Charging a neutral body by touching it with a charged body. 12 Mahendra singh PGT (PHY)Gold leaf electroscope: Gold leaf electroscope A simple apparatus which is used to detect charge on a body is the gold-leaf Electroscope. Construction: - It consists of a vertical metal rod housed in a box, with two thin gold leaves attached to its bottom end. 13 Mahendra singh PGT (PHY)BASIC PROPERTIES OF ELECTRIC CHARGE: BASIC PROPERTIES OF ELECTRIC CHARGE 1. Charge is conserved: The total charge of the isolated system is always conserved . 2. Quantization of charge: i.e. An object may have a charge ±e, or ± 2e, or ± 3e, etc but not say ± 1.5e. Thus Q= ± ne 3. Additivity of charges 14 Mahendra singh PGT (PHY)CONDUCTORS AND INSULATORS: CONDUCTORS AND INSULATORS Conductor- Those materials which allow electricity to pass through them easily are called conductors . For example- ( i ) silver (ii) copper (iii) aluminum etc. Insulator- Those materials which do not allow electricity to pass through them easily are called insulators. For example- ( i ) wood (ii) plastic (iii) sand etc. 15 Mahendra singh PGT (PHY)Questions: What does q1 + q2 =o signify in electrostatics? [CBSE 2001] What is quantization of charges? If a tiny particle is given a charge; does its mass increase or decrease ? Write any two properties of electric charges? A conductor carries a charge -9.6 x 10-17C. How many free electrons are in the conductor? Questions 16 Mahendra singh PGT (PHY)Electrostatics force: Electrostatics force As similar charges repel each other and opposite charges attracts each other .That force for of repulsion and attraction between two charges particle is called electrostatics force. 17 Mahendra singh PGT (PHY)Coulomb’s Law for Electrostatics: Coulomb’s Law for Electrostatics According to coulomb, “ The electrostatics force between two charge particles is equal to product of their charges and inversely proportional to square of their distance between their centers .” 18 Mahendra singh PGT (PHY)Properties of Electric force: Properties of Electric force It is force of attraction as well as force of repulsion. It is long range force. It is conservative force. It is central force. It obeys inverse square law. It obeys action and reaction law. 19 Mahendra singh PGT (PHY)Dielectric Constant (k): Dielectric Constant (k) K= Electric force in vacuum /Electric force in medium The dielectric constant of given medium is defined as that ration of electric force applied between two electric charges in vacuum to electric force applied between same charges at same distance in given medium. 20 Mahendra singh PGT (PHY)Questions: Questions The force acting between two point charges q1 & q2 kept at some distance apart in air is attractive or repulsive when ( i ) q1q2>0 (ii)q1q2<0 [CBSE 2007] Define dielectric constant of a medium in terms of force between electric charges. [CBSE-1997] The force between two point charges kept at a distance r apart in air is F. If the same charges are kept in water at the same distance, how does the force between them change ? [CBSE1997] 21 Mahendra singh PGT (PHY)Electric Field: Electric Field The space and region around the electric charge in which other charge particles experience force is known as electric field. 22 Mahendra singh PGT (PHY)Electric field intensity: Electric field intensity The electric field intensity at any given point in electric field is defined as force experienced by a unit charge particle at that point. SI Unit – Newton/coulomb It is vector quantity 23 Mahendra singh PGT (PHY)Electric field lines: Electric field lines Electric field lines or lines of force provide a map of the electric field in the space surrounding electric charges. “Electric field lines are defined as the path traced by unit positive charge in electric field, if it is free to do so.” 24 Mahendra singh PGT (PHY)Properties of electric field lines: Properties of electric field lines The lines are hypothetical lines which originate from a positive charge (or infinity) and end at a negative charge (or infinity). No two field lines can cross each other. because if they do so there two directions of electric field at point of intersection which is not possible. The line are perpendicular to the surface of the charge The tangent to an electric field line at a point in space gives the direction of the electric field at that point. 25 Mahendra singh PGT (PHY) Magnetic field lines of positive charge (q>0) : Magnetic field lines of positive charge (q>0) 26 Mahendra singh PGT (PHY) Electric field lines due to negative charge (q<0) : Electric field lines due to negative charge (q<0) 27 Mahendra singh PGT (PHY)Electric field lines due to electric dipole: Electric field lines due to electric dipole 28 Mahendra singh PGT (PHY)Electric field lines due to uniform electric field: Electric field lines due to uniform electric field 29 Mahendra singh PGT (PHY)Questions: Questions The electric field lines never cross each other, why? [ CBSE 1995C] Draw lines of force to represent uniform electric field . [ CBSE 1995,2000,1999,2008] Which physical quantity has unit N/C ? Is it a vector or a scalar quantity ? [ CBSE 2010,2000C] Two point charge q= +3 μ C and q= -3 μ C are located at points A and B , 20 cm apart in vacuum. Find the electric field at the mid point of the line AB joining the two charges .[2003] 30 Mahendra singh PGT (PHY)Electric flux: Electric flux The electric flux through a planar area is defined as the electric field times the component of the area perpendicular to the field. 31 Mahendra singh PGT (PHY)ELECTRIC DIPOLE: ELECTRIC DIPOLE An electric dipole is a pair of equal and opposite point charges q and – q, separated by a distance 2 a . By convention, the direction from – q to q is said to be the direction of the dipole. 32 Mahendra singh PGT (PHY)ELECTRIC DIPOLE MOMENT: ELECTRIC DIPOLE MOMENT The product of either charge and length of electric charge is called electric dipole moment P= q(2l) It is vector quantity It’s unit is Coulomb metre 33 Mahendra singh PGT (PHY)Electric Field due to an Electric Dipole: Electric Field due to an Electric Dipole ( it Axial point- 34 Mahendra singh PGT (PHY)Electric Field due to an Electric Dipole: Electric Field due to an Electric Dipole (ii)At Equatorial point 35 Mahendra singh PGT (PHY)DIPOLE IN A UNIFORM EXTERNAL FIELD: DIPOLE IN A UNIFORM EXTERNAL FIELD Net force- F =(+ qE - qE )=0 No translatory motion Torque- τ = P x E 36 Mahendra singh PGT (PHY)Questions: Questions Define electric dipole moment. Is it a scalar of a vector quantity? [ AI CBSE 2006, 2009] An electric dipole of dipole moment 20 x 10-6 C is enclosed by closed surface. What is the net electric flux coming out of this surface?[CBSE 2005] The distance of field point, on the equatorial plane of a small electric dipole is halved. By what factor does the electric field due to the dipole change ? [CBSE 2004 C] 37 Mahendra singh PGT (PHY)GAUSS’S LAW: GAUSS’S LAW The electric flux Φ E through any closed surface is equal to the net charge inside the surface, Q inside, divided by ε 0 :- 38 Mahendra singh PGT (PHY)Electric Field due to an infinitely long straight uniformly charged wire: Electric Field due to an infinitely long straight uniformly charged wire 39 Mahendra singh PGT (PHY)Electric Field due to a uniformly charged thin spherical shell: Electric Field due to a uniformly charged thin spherical shell Field outside the shell:- Field inside the shell:- 40 Mahendra singh PGT (PHY)Electric Field due to a uniformly charged infinite plane sheet: Electric Field due to a uniformly charged infinite plane sheet 41 Mahendra singh PGT (PHY)Electric field due to charged cylinder: Electric field due to charged cylinder 42 Mahendra singh PGT (PHY)Questions: Questions If the radius of the Gaussian surface enclosing a charge is halved , how does the electric flux through the Gaussian surface change?[2008] State Gauss theorem in electrostatics . Apply this theorem to obtain the expression for the electric field at a point due to an infinitely ling, thin, uniformly charged straight wire of linear charge density λ C/m.{[05,07,08,09] Mahendra singh PGT (PHY) 43Slide 44: 44 Mahendra singh PGT (PHY)