Electric Fields
Q. Define an electric field.
A region of space in which charged particles are subject to an electrostatic force.
Q. What units does an electric field have?
An electric field is quantitatively expressed as the force per unit positive charge i.e. N/C.
Note that the magnitude of the electric field is a vector quantity, since it has direction.
Q. Which direction do the field lines point?
Positive to negative, the lines always point away from a positive charge and towards a negative charge.
Q. What effect does distance have on the strength of the electrostatic force?
The greater the distance, the weaker the force.
Q. What effect does a uniform electric field have on the motion of charged particles?
It causes positively charged particles to accelerate towards the negative pole and negatively charged particles to accelerate towards the positive pole of the electric field.
Q. What is Coulomb's Law?
The force between any two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
Q. Define permittivity.
The ability of a material to transmit an electric field. (A measure of how easily the atoms become polarised.)
Q. Define potential at a point in an electric field.
The work done per unit charge in moving a positive test charge from infinity to that point in the electric field.
Q. What can the motion of charged particles in an electric field be modelled as?
Projectile motion: the two components of velocity are independent of each other. The velocity perpendicular to the field is not affected, whereas the velocity parallel to the field is.
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