4.2.1 Electrostatic Fields Flashcards
What is electrostatic charging?
Electrostatically charging an object involves the redistribution, addition or removal of electrons.
what are the two ways of charging an object?
- Charging by friction. This is the process of friction generates energy to remove some electrons from the surface of material and place them onto the duster.
- Charging by induction. The electrons redistribute themselves onto the leaves of the electroscope. A positive charge is induced on the top plate of the electroscope.
What is an electric field?
It is used to help explain non-contact forces between charges.
What are field lines?
A line that indicates the direction of the force.
What is the field due to point charge for a positive point charge?
The field around a positive charge has arrows directed away from the centre.
A positive charge placed in the field would be repelled.
What is the field due to point charge for a negative point charge?
The field around a negative charge has arrows directed towards the centre.
A positive charge placed in the field would be attracted.
What is the field due to point charge for charges of different magnitude?
Greater the density of field lines, the larger the magnitude.
What is the field between two point charges for unlike point charges?
What is the field between two point charges for like point charges?
The field between two like charges has a point where the field is zero.
What is the field between two parallel plates?
The field lines are straight and parallel to another. This means that the field strength is uniform through except at the edges - slightly less strength.
Define Electric Field Strength and state the units.
It is the force per unit charge.
E = F/q
units: NC-1
How is the magnitude of electric field strength affected by variation in charge and distance?
As charge increases E increases, E is proportional to Q. As r increases E decreases. E is proportional to 1/r squared, as in Coulomb’s law.
What is the definition of r?
Radical distance from point charge (m)
What is the definition of Q?
Magnitude of point charge (C)
How is electric field strength another example of the inverse square law?
The relationship between E and r is an example of the law. If r doubles then E becomes 1/4 of it previous strength. If r is halved then E becomes 4 times greater.
