Chapter 8 ~ Electric Fields

Question 1

4 characteristics of electric charge :

Answer 1

1. Objects are usually electrically neutral but they may become electrically charged
2. 2 types of charge:°positive
   °negative
3. Opposite charges attract and like charges repel
4. A charged object may also be able to attract an uncharged one ; this is a result of electrostatic induction

Question 2

3 examples where static electricity is useful

Answer 2

1. Process of photocoping
2. In dust precipitation to clean up industrial emissions
3. Crop spraying

Question 3

How is electric shock formed ?

Answer 3

It is formed when static electric charge builds up and gives a shock when it discharges

Question 4

What is electric charge?

Answer 4

A property of a body that gives rise to a force on the body when it is within an electric field

Question 5

Friction can transfer….?

Answer 5

Electrons between materials

Question 6

Why do electrons transfer and not protons?

3 reasons

Answer 6

1. They are on the outside of atoms, so therefore they are less strongly held within a material than protons
2. Electrons may be free to move about within a material
3. Electrons may be relatively weakly bound within atoms

Question 7

Definition of a field of force

Answer 7

A region of space where an object feels a forces, the force may be gravitational, electric, magnetic, etc.

Question 8

Name the 3 main types of fields of force and what they act upon:

Answer 8

1. electric fields - act on objects with electric charge
2. magnetic fields - act on magnetic materials, magnets and moving charges (including electric currents)
3. Gravitational fields - act on objects with mass

Question 9

Definition of field lines ⚟

Answer 9

Lines ⚟ drawn to represent the strength and direction of a field of force

Question 10

What tells us how strong the field is?

What will lead to the strongest field

Answer 10

The separation of the lines.

Strongest field has closest lines ⚟

Question 11

Field line’s direction is always from…

Answer 11

Positive to negative

Question 12

A uniform field has the same (……..) at all points. Fill in the word.

Answer 12

Strength 💪

Question 13

An example of a uniform electric field that we learn about in AS

Answer 13

An electric field between oppositely charged parallel plates

Question 14

A radial field spreads out in all directions. Give 2 examples…

Answer 14

1. an electric field around a point charge

2. A charged sphere

Question 15

What are the 3 most important electric fields?

Answer 15

1. A uniform electric field (e.g.is produced between two oppositely charged plates)
2. A radial electric field (e.g. surrounds a charged sphere)
3. The electric field between a charged sphere and an earthed plate 🌎

Question 16

Definition of an electric field

Answer 16

A region of space in which a unit positive charge experiences a force. It is an example of a field of force.

Question 17

Definition of electric field strength 💪 (symbol E)

And its unit?

Answer 17

° 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)

Question 18

The 2 formula for electric field strength 💪 are?

Answer 18

❤️1. E=F/Q❤️

F-force
Q-charge

❤️2. E=V/d❤️

V-voltage ⚡
d- separation between plates

Question 19

The strength 💪 of a uniform electric field depends on 2 things, namely…

Answer 19

1. The voltage ⚡ between the plates - the higher 👆 the voltage ⚡ the stronger the the field (directly proportional, E♉V )
2. The separation between the plates - the greater their separation, the weaker the field (inversely proportional, E ♉ 1/d)

♉-means proportional

Question 20

Field lines ⚟ travel from a region of…

Answer 20

Higher 👆 potential to a region of lower 👇 potential.

More “positive” to less “ positive”.
Less “negative” to more “negative”
From “positive” to “negative”

Question 21

Quick definition of electric field strength 💪

Answer 21

Force per unit positive charge

Question 22

1Vm^-1=

Answer 22

1NC ^-1

Question 23

A uniform field refers to the fact that

Answer 23

The electric field strength is the same at any point of a field as well as the force on the charge is constant

Question 24

Work done by an electric field =

2 equations

Answer 24

W= VQ

W=F×d

Question 25

A moving electron in a uniform electric field trajectory can be described as…

Answer 25

A parabolic (curved) path. Due to repulsive and attractive forces on the charge.