Chapter 1: Electric Current (3 Sec 1) PDF

MR / Michael 1  Electric current: It is the flow of electric charges through a conductor. {There must be potential difference between terminals of conductor} Direction of electric current 1- Conventional current: It is the flow of positive charges from(+ve)to (-ve)pole {We w...

MR / Michael 1  Electric current: It is the flow of electric charges through a conductor. {There must be potential difference between terminals of conductor} Direction of electric current 1- Conventional current: It is the flow of positive charges from(+ve)to (-ve)pole {We will use this direction through our syllabus} 2-Electronic current: It is the flow of electrons from (-ve) to (+ve) terminal  Conditions to obtain electric current: 1-Electric source {To produce potential difference between two terminals of conductor} 2-Closed circuit Characteristics of an electric current: 1-Electric current intensity (I ) 2-Electric potential difference (P.D) 3-Electrical resistance (R) MR / Michael 2 It is the quantity of electric charges (Q) in coulomb passing through a given cross sectional area in one second. Q {quantity of charges} {Electric current intensity}I= t {Time per second} OR Q  I x t Coulomb Ampere Second What is meant by Ampere? It is the current intensity that produced due the passage of 1 coulomb of quantity of charges through conductor in one second. Unit of What is the physical quantity and equivalent the following 1- Ampere.sec.  Physical quantity Quantity of charge  Equivlent unit Coulomb 2- Coulomb Ampere  Physical quantity Electric current intensity  Equivlent unit Second Important Hint: @Where n is the number of electron passing through Q= n X e Conductor in one second  e :it is the charge of electron e  1.6x 1019 coulomb  Electric current intensity is measured by device called "Ammeter" which is connected inside circuit on series to record the electric current which passes through the whole circuit  Problem (1):  A current intensity of 3.2 A passes through a conductor.Find the number of electrons that passes across its cross section during 3 seconds given that the charge of an electron e=1.6x10-19 coulomb.  Solution 3.2x 3  Q= I x t = ne so 3.2 x 3= nx1.6 x10-19  n= 19  6 x 1019 electrons 1.6x 10 MR / Michael 3   Problem (2):An electron rotates around the nucleus of a hydrogen atom making 6.6x1015 revolution per second.Calculate the current intensity resulting from it knowing that the charge of electron=1.6x10-19 coulomb.  Solution q= Ix t = n x e  I x1 = 6.6x1015 x 1.6x 1019  I = 10.56 x1014 A Problem (3):If the flow rate of electrons in wire X is 1020 electron/sec. and its flow rate in wire Y is 2x1020 electron/sec. then the ratio between current intensity (Ix /Iy ). 1 1 2 1 A) B) C) D) 1 2 1 4 Solution:  Ne Nx Ny I   10 20 and  2 x10 20 t t t Ix Nx t 1020 1   x   Iy t Ny 2 x10 20 2 Problem (4): Based on Bohr model for the hydrogen atom,the electron move in circular path of radius 0.53 A0 with speed of 2.2x106 m/s. the current intensity due to the motion of the electron equals…………………. A)03.141 mA B)6.282mA C)1.166 mA D)1.057 mA Solution:  Ne d (circumference) 2 r 2 r I V   t= N= 1 electron t t t V  e  1.6 x1019 C 1x1.6 x1019 1x1.6 x1019  I=  x2.2 x106  0.001057 A  1.057mA 2 r 2 x3.14 x0.53x10 10 V MR / Michael 4 Quiz:(1) MR / Michael 5 5-The opposite diagram shows a section of a Conductor that carries an electric current ,so Which of the following choices shows the relation among current intensities at the cross section x,y and z? A) Ix > I y >Iz B) Ix = I y =Iz C) Ix < I y >Iz D) Ix < I y