Uniform electric fields Flashcards
Electric charge
A property of an object that gives rise to a force on the body when the body is in an electric field.
Mechanism of electrostatic induction
It is usually electrons that are involved in moving within a material, or from one material to another. This is because electrons, which are on the outside of atoms, are less strongly held within a material than are protons.
How to produce and observe an electric field (general)?
To produce an electric field, we need unbalanced charges (as with the charged plastic). To observe the field, we need to put something in it that will respond to the field (as your hair responds).
ELectric field
A region where a charged object experiences a force.
Field of force
A charged object experiences a force in an electric field. This is what an electric field is. We say that there is an electric field anywhere where an electric charge experiences a force. An electric field is a field of force.
Types of fields
- electric fields – act on objects with electric charge
- magnetic fields – act on magnetic materials, magnets and moving charges (including electric currents)
- gravitational fields – act on objects with mass
Electric field strength (at a point)
The electric field strength at a point is defined as the force per unit charge exerted on a stationary positive charge at that point.
Electric field strength at a point equation
E = F / Q (Unit : NC−1)
Field lines
Field lines are drawn to represent an electric field. They show the direction of the force on a positive charge placed at a point in the field.
Strength of a uniform field between two parallel metal plates Equation
E = V / d
Derive F / Q = V / d
Work done = Fd and Energy transformed = VQ
substituting gives : Fd = VQ
and rearranging gives : F / Q = V / d
Path followed by an electron between parallel metal plates (top being negative and bottom being positive) as it enters from horizontal left
If the electron were stationary, it would accelerate directly downwards. However, the electron is moving to the right. Its horizontal velocity will be unaffected by the force, but as it moves sideways it will also accelerate downwards. It will follow a curved path, as shown. This curve is a parabola.
Force experienced by an electron in an electric field
The force on the electron is the same at all points between the plates, and it is always in the same direction.
