Static Electricity

Lesson Objective At the end of the lesson, students should be able to: State that there are positive and negative charges and that charges is measured in coulombs State that unlike charges attract and like charges repel Describe an electric field as a region in which an electric charge experiences a force Draw the electric field of an isolated point charge and recall that the direction of the field lines gives the direction of the force acting on a positive test charge Draw electric field pattern between two isolated point charges

What’s Static Electricity Static Electricity Safety Video - Fire Explosion shown http://www.youtube.com/watch?v=5TcNDozWQiM

Electrostatics Two types of electric charge Positive (+) Negative (-) SI unit for electric charge is coulomb (C) Law of charges Like charges repel and unlike charges attract

Laws of Electrostatics When the charges are close  force is strong When the charges are further apart  forces are weak

Examples

Electrostatic Fun with Science Bob http://www.youtube.com/watch?v=T0J5q43MSw8

Electric Field – isolated charges An electric field is a region which an electric charge experiences a force Electric field line is the path a positive charge would take if it is free to move Direction of electric field lines gives direction of force acting on a positive test charge

Electric Field – isolated charges Positive Charge Negative Charge Arrows are pointing towards the charge Field lines are close, nearer to the point Arrows are pointing away from the charge Field lines are close, nearer to the point

Electric Field – between 2 charges To sketch combined electric field, the following rules must be applied: Lines must begin on positive charges and end on negative charges Number of lines drawn leaving positive charge or ending on negative charge is proportional to magnitude of charge No 2 field lines can cross each other

Electric Field – isolated charges The number of field lines is proportional to the charge The greater the charge  the greater the number of field lines

Electric Field – between 2 charges Electric lines of forces are closer to each other in a stronger electric field

Electric Field Electric field between parallel oppositely-charged plates is uniform at the central region