Electric Fields and Potential. Electric field – a force field that fills the space around every electric charge or charges Example:. Electron. Proton. An electric field has both magnitude and direction Therefore, an electric field can be represented using… VECTORS!!!.
Electric Field = Force ÷ charge
E = F ÷ q
A 0.5 C charge experiences a force of 20 N when placed in an electric field.
What is the strength of the electric field, E?
E = F ÷ q =
20 N ÷ 0.5 C =
The electric field in a television picture tube is around 10,000 N/C.
The electric field at the location of the electron in a Hydrogen atom is 500,000,000,000 N/C!
The further you go from an electric charge, the weaker the field becomes.
There is no way to shield from gravity, but there is a way to shield from an electric field….
Surround yourself or whatever you wish to shield with a conductor (even if it is more like a cage that a solid surface)
That’s why certain electric components are enclosed in metal boxes and even certain cables, like coaxial cables have a metal covering.
The covering shields them from all outside electrical activity.
Michael Faraday demonstrated that the electrostatic charge only resides on the exterior of a charged conductor, and exterior charge has no influence on anything enclosed within a conductor.
This was one of many contributions he made to electromagnetic theory.
Electrons repel toward the outside of any conducting surface
Net charge inside is zero
Electrons flow outward evenly, but pile up on sharp corners
Shielding is important in electronic devices such as televisions and computers
Person in a car hit by artificial lightning. The lightning strikes the car and jumps to the ground bypassing the front tire arcing from the axle to the ground.
Rub a balloon on your hair and it becomes negatively charged, perhaps to several thousand volts.
Does this mean that there’s a lot of electrical energy?
Well, the charge transferred to the balloon is typically less than a millionth of a Coulomb.
There’s a LOT of difference between Voltage and Energy!
High Voltage does not necessarily mean that there’s a lot of useful energy or that something is dangerous.
The Electric Potential (Voltage), V, changes as you move from one place to another in an electric field
The change in Potential (“pressure”), called the “Potential Difference” is given by
DV = Ed
For example, the potential difference between two locations separated by 3 meters in a 4000 N/C electric field is given by
DV = Ed = 4000 N/C x 3 m =
A charge placed in an electric field will experience an electric force,
F = Eq
This force will make the charge accelerate according to Newton’s Second Law
F = ma
The Electric Field can also be determined by using Coulomb’s Law: