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Page 1 CURRENT ELECTRICITY - I 1. Electric Current 2. Conventional Current 3. Drift Velocity of electrons and current 4. Current Density 5. Ohm’s Law 6. Resistance, Resistivity, Conductance & Conductivity 7. Temperature dependence of resistance 8. Colour Codes for Carbon Resistors 9. Series and Parallel combination of resistors 10. EMF and Potential Difference of a cell 11. Internal Resistance of a cell 12. Series and Parallel combination of cells Page 2 CURRENT ELECTRICITY - I 1. Electric Current 2. Conventional Current 3. Drift Velocity of electrons and current 4. Current Density 5. Ohm’s Law 6. Resistance, Resistivity, Conductance & Conductivity 7. Temperature dependence of resistance 8. Colour Codes for Carbon Resistors 9. Series and Parallel combination of resistors 10. EMF and Potential Difference of a cell 11. Internal Resistance of a cell 12. Series and Parallel combination of cells Electric Current: The electric current is defined as the charge flowing through any section of the conductor in one second. I = q / t (if the rate of flow of charge is steady) I = dq / dt (if the rate of flow of charge varies with time) Different types of current: I t 0 a b c d) Alternating current whose magnitude varies continuously and direction changes periodically a) Steady current which does not vary with time b) & c) Varying current whose magnitude varies with time d Page 3 CURRENT ELECTRICITY - I 1. Electric Current 2. Conventional Current 3. Drift Velocity of electrons and current 4. Current Density 5. Ohm’s Law 6. Resistance, Resistivity, Conductance & Conductivity 7. Temperature dependence of resistance 8. Colour Codes for Carbon Resistors 9. Series and Parallel combination of resistors 10. EMF and Potential Difference of a cell 11. Internal Resistance of a cell 12. Series and Parallel combination of cells Electric Current: The electric current is defined as the charge flowing through any section of the conductor in one second. I = q / t (if the rate of flow of charge is steady) I = dq / dt (if the rate of flow of charge varies with time) Different types of current: I t 0 a b c d) Alternating current whose magnitude varies continuously and direction changes periodically a) Steady current which does not vary with time b) & c) Varying current whose magnitude varies with time d Conventional Current: Conventional current is the current whose direction is along the direction of the motion of positive charge under the action of electric field. + + + + - - - - + + + + - - - - I Drift Velocity and Current: Drift velocity is defined as the velocity with which the free electrons get drifted towards the positive terminal under the effect of the applied electric field. I v d = - (eE / m) t - - - v d E l A I = neA v d v d = a t v d - drift velocity, a – acceleration, t – relaxation time, E – electric field, e – electronic charge, m – mass of electron, n – number density of electrons, l – length of the conductor and A – Area of cross-section Current is directly proportional to drift velocity. Conventional current due to motion of electrons is in the direction opposite to that of motion of electrons. + + + I - - - Page 4 CURRENT ELECTRICITY - I 1. Electric Current 2. Conventional Current 3. Drift Velocity of electrons and current 4. Current Density 5. Ohm’s Law 6. Resistance, Resistivity, Conductance & Conductivity 7. Temperature dependence of resistance 8. Colour Codes for Carbon Resistors 9. Series and Parallel combination of resistors 10. EMF and Potential Difference of a cell 11. Internal Resistance of a cell 12. Series and Parallel combination of cells Electric Current: The electric current is defined as the charge flowing through any section of the conductor in one second. I = q / t (if the rate of flow of charge is steady) I = dq / dt (if the rate of flow of charge varies with time) Different types of current: I t 0 a b c d) Alternating current whose magnitude varies continuously and direction changes periodically a) Steady current which does not vary with time b) & c) Varying current whose magnitude varies with time d Conventional Current: Conventional current is the current whose direction is along the direction of the motion of positive charge under the action of electric field. + + + + - - - - + + + + - - - - I Drift Velocity and Current: Drift velocity is defined as the velocity with which the free electrons get drifted towards the positive terminal under the effect of the applied electric field. I v d = - (eE / m) t - - - v d E l A I = neA v d v d = a t v d - drift velocity, a – acceleration, t – relaxation time, E – electric field, e – electronic charge, m – mass of electron, n – number density of electrons, l – length of the conductor and A – Area of cross-section Current is directly proportional to drift velocity. Conventional current due to motion of electrons is in the direction opposite to that of motion of electrons. + + + I - - - Current density: Current density at a point, within a conductor, is the current through a unit area of the conductor, around that point, provided the area is perpendicular to the direction of flow of current at that point. J = I / A = nev d In vector form, I = J . A Ohm’s Law: The electric current flowing through a conductor is directly proportional to the potential difference across the two ends of the conductor when physical conditions such as temperature, mechanical strain, etc. remain the same. I V I a V or V a I or V = R I V I 0 Page 5 CURRENT ELECTRICITY - I 1. Electric Current 2. Conventional Current 3. Drift Velocity of electrons and current 4. Current Density 5. Ohm’s Law 6. Resistance, Resistivity, Conductance & Conductivity 7. Temperature dependence of resistance 8. Colour Codes for Carbon Resistors 9. Series and Parallel combination of resistors 10. EMF and Potential Difference of a cell 11. Internal Resistance of a cell 12. Series and Parallel combination of cells Electric Current: The electric current is defined as the charge flowing through any section of the conductor in one second. I = q / t (if the rate of flow of charge is steady) I = dq / dt (if the rate of flow of charge varies with time) Different types of current: I t 0 a b c d) Alternating current whose magnitude varies continuously and direction changes periodically a) Steady current which does not vary with time b) & c) Varying current whose magnitude varies with time d Conventional Current: Conventional current is the current whose direction is along the direction of the motion of positive charge under the action of electric field. + + + + - - - - + + + + - - - - I Drift Velocity and Current: Drift velocity is defined as the velocity with which the free electrons get drifted towards the positive terminal under the effect of the applied electric field. I v d = - (eE / m) t - - - v d E l A I = neA v d v d = a t v d - drift velocity, a – acceleration, t – relaxation time, E – electric field, e – electronic charge, m – mass of electron, n – number density of electrons, l – length of the conductor and A – Area of cross-section Current is directly proportional to drift velocity. Conventional current due to motion of electrons is in the direction opposite to that of motion of electrons. + + + I - - - Current density: Current density at a point, within a conductor, is the current through a unit area of the conductor, around that point, provided the area is perpendicular to the direction of flow of current at that point. J = I / A = nev d In vector form, I = J . A Ohm’s Law: The electric current flowing through a conductor is directly proportional to the potential difference across the two ends of the conductor when physical conditions such as temperature, mechanical strain, etc. remain the same. I V I a V or V a I or V = R I V I 0 Resistance: The resistance of conductor is the opposition offered by the conductor to the flow of electric current through it. R = V / I Resistance in terms of physical features of the conductor: I = neA | v d | I = neA (e |E| / m) t ne 2 At m V l I = ne 2 At V I = ml ne 2 t A R = m l A R = ? l where ? = ne 2 t m is resistivity or specific resistance Resistance is directly proportional to length and inversely proportional to cross-sectional area of the conductor and depends on nature of material. Resistivity depends upon nature of material and not on the geometrical dimensions of the conductor.Read More
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