L3 Physical Science Static Electricity 2

Static Electricity Lecturer: Semase M.P Physical Science L3 Downloaded Sefikeng Campus from hlayiso.com

Subject outcome State, analyse and apply principles of static electricity Learning outcomes  Define coulombs law and apply it to calculate the force between the charges  Identify and draw the electric field around single charges and groups of charges  Calculate the electric field around a charge and between parallel plates  Define and apply electrical potential energy and electrical potential Downloaded from hlayiso.com

Introduction • We know from previous work on electrostatics that like charges repel each other and unlike charges attract each other • Attraction and repulsion are forces that objects exert on each other • We can calculate the size of these forces by using the equation for coulombs law • The point charges will exert an attractive or repulsive force on each other • The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them Downloaded from hlayiso.com

Calculating the force between charges • We can use the equation for coulombs law to calculate the size of the force exerted between charges • In some cases, more than two charges exert forces on each other • To solve this kind of problem. Find the forces exerted by each of the two charges individually and then determine the resultant force of the two forces Downloaded from hlayiso.com

Test charges and electric fields • The force between charges occurs because the electric fields of the charges interact with one another • An electric field is a region in space in which a positive test charge experiences a force • In order to test for an electric field we use a test charge • A test charge is a small charge that does not affect the electric field in which it is placed and it is always positive Downloaded from hlayiso.com

Electric fields Like charges Unlike charges Downloaded from hlayiso.com

Summary • When you use coulombs law, in the equation charge must be in coulombs and distance in meters • An electric field is a region in space in which a positive test charge experiences a force • We can use a test charge to test the presence of an electric field • Electrical potential difference is the work done per unit charged moved between the points Downloaded from hlayiso.com

Assessment activity • State coulombs law in words(2) • Give the meaning and unit of coulombs law (3) • Draw a diagram of electric field around two positive charges that are some distancing apart(5) • What is meant by test charge (2) • Define electric field strength(2) Downloaded from hlayiso.com