Faraday’s Model The field of a point charge extended vectors into lines radiating from the point. These are called field lines.
Field Lines vs Vector The electric field is a vector quantity. Measured at each pointMeasured at each point Show magnitude and directionShow magnitude and direction The field lines connect separate vectors. Show the path of motion for a test chargeShow the path of motion for a test charge
Field Line Properties The field vector is tangent to the field line at each point. The density of field lines is related to the magnitude of the field. Field lines cannot cross each other.
Dipole The field lines for two equal and opposite point charges form a special pattern called a dipole. All the lines start at the positive charge and end at the negative charge.
Conductor Fields Charges move to the surface of a conductor. The field lines remain perpendicular to the surface of the conductor. True for straight or curved Inside the conductor the field is zero.
Inside Space The inside of a conductor has no field because the charges have moved to the surface and canceled the field inside. If there are no isolated charges in a space surrounded by a conductor the field is zero inside.
Faraday Cage The conductor doesn’t need to be solid to block a field. The enclosure is a Faraday cage. Field between the generators and the cageField between the generators and the cage Not within the cageNot within the cage next