Chapter 8 ~ Electric Fields Flashcards
Definitions, formula and key ideas
4 characteristics of electric charge :
- Objects are usually electrically neutral but they may become electrically charged
- 2 types of charge:°positive
°negative - Opposite charges attract and like charges repel
- A charged object may also be able to attract an uncharged one ; this is a result of electrostatic induction
3 examples where static electricity is useful
- Process of photocoping
- In dust precipitation to clean up industrial emissions
- Crop spraying
How is electric shock formed ?
It is formed when static electric charge builds up and gives a shock when it discharges
What is electric charge?
A property of a body that gives rise to a force on the body when it is within an electric field
Friction can transfer….?
Electrons between materials
Why do electrons transfer and not protons?
3 reasons
- They are on the outside of atoms, so therefore they are less strongly held within a material than protons
- Electrons may be free to move about within a material
- Electrons may be relatively weakly bound within atoms
Definition of a field of force
A region of space where an object feels a forces, the force may be gravitational, electric, magnetic, etc.
Name the 3 main types of fields of force and what they act upon:
- 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
Definition of field lines ⚟
Lines ⚟ drawn to represent the strength and direction of a field of force
What tells us how strong the field is?
What will lead to the strongest field
The separation of the lines.
Strongest field has closest lines ⚟
Field line’s direction is always from…
Positive to negative
A uniform field has the same (……..) at all points. Fill in the word.
Strength 💪
An example of a uniform electric field that we learn about in AS
An electric field between oppositely charged parallel plates
A radial field spreads out in all directions. Give 2 examples…
- an electric field around a point charge
2. A charged sphere
What are the 3 most important electric fields?
- A uniform electric field (e.g.is produced between two oppositely charged plates)
- A radial electric field (e.g. surrounds a charged sphere)
- The electric field between a charged sphere and an earthed plate 🌎
Definition of an electric field
A region of space in which a unit positive charge experiences a force. It is an example of a field of force.
Definition of electric field strength 💪 (symbol E)
And its unit?
° the electric field strength at a point is the force per unit positive charge exerted(acting) on a stationary positive charge at that point.
Unit : newton’s per coulomb ( NC^-1)
The 2 formula for electric field strength 💪 are?
❤️1. E=F/Q❤️
F-force
Q-charge
❤️2. E=V/d❤️
V-voltage ⚡
d- separation between plates
The strength 💪 of a uniform electric field depends on 2 things, namely…
- The voltage ⚡ between the plates - the higher 👆 the voltage ⚡ the stronger the the field (directly proportional, E♉V )
- The separation between the plates - the greater their separation, the weaker the field (inversely proportional, E ♉ 1/d)
♉-means proportional
Field lines ⚟ travel from a region of…
Higher 👆 potential to a region of lower 👇 potential.
More “positive” to less “ positive”.
Less “negative” to more “negative”
From “positive” to “negative”
Quick definition of electric field strength 💪
Force per unit positive charge
1Vm^-1=
1NC ^-1
A uniform field refers to the fact that
The electric field strength is the same at any point of a field as well as the force on the charge is constant
Work done by an electric field =
2 equations
W= VQ
W=F×d
A moving electron in a uniform electric field trajectory can be described as…
A parabolic (curved) path. Due to repulsive and attractive forces on the charge.
