1. Unit 2 Particles and Waves Electric Fields and Movements of Charge
CfE Higher Physics
Unit 2
Particles and Waves
Electric Fields and Movements of Charge

2. Learning Intentions
To be able to state that, in an electric field, an electric charge experiences a force.
State that an electric field applied to a conductor causes the free electric charges in it to move.

3. Electric Fields
An electric field is a region of space in which charged particles experience a force.
When an electric field is applied to a conductor the free electric charges are caused to move.
Electric fields can be represented by field lines. These lines show the direction in which a positive charge experiences the force. The closer together the lines the stronger the force.

4. Field Patterns Positive point charge Negative point charge+ -
Positive point charge
Negative point charge + - + -
Positive and negative point charges
Parallel charged plates

5. Electric Fields Charges experience a FORCE in electric fields.
When an electric field is applied to a conductor the free electric charges are caused to move.
Electric fields can be represented by field lines. These lines show the direction in which a positive charge experiences the force. The closer together the lines the stronger the force.

6. Field Patterns Positive point charge Negative point charge+ -
Positive point charge
Negative point charge + - + -
Positive and negative point charges
Parallel charged plates

7. Success criteria
To be able to state that, in an electric field, an electric charge experiences a force.
State that an electric field applied to a conductor causes the free electric charges in it to move.

8. Learning Intentions
State that work, W, is done when a charge, Q, is moved in an electric field.
State that the potential difference (V) between two points is a measure of the work done in moving one coulomb of charge between the two points
State that if one joule of work is done moving one coulomb of charge between two points, the potential difference between the points is one volt.
State the relationship V = W/Q.
Carry out calculations involving the relationship V = W/Q
Calculate the speed of a charged particle accelerated in an electric field using the relationship QV = ½ mv2.

9. Potential Difference
When a charged particle is moved in an electric field work is done. Charges can accelerate in electric fields.
The potential difference (p.d.) between two points is a measure of the work done in moving one coulomb of charge between the two points.
The SI unit of potential difference is the volt, V.
V = Q Ew
W = QV

10. Voltage definition
V = Q W
From the equation: we are able to state the definition of 1 volt:
When 1 Joule of work is done in moving a 1 Coloumb of charge between two points there in a potential difference of 1 Volt.
Charges can accelerate in an electric field.
V= voltage (V)
W = work done (J)
Q = charge (C)
W = QV

11. Potential difference and kinetic energy

12. Potential difference and EK

13. Worked Example
A particle with a mass of 3.6 x10-6 kg and a charge of x10-6 C is accelerated from rest through a potential difference of 20 kV. Calculate the final velocity of the particle.
Work done = Increase in kinetic energy
QV = ½mv2
4.8 x10-6 x 20,000 = ½ x 3.6 x10-6 v2
v2 = 5.33 x104
v = 231 ms-1

14. The Electron Volt
Sometimes we measure energy of charges in electron volts, eV.
1eV = 1.6x10-19 C x 1V = 1.6x10-19 J
(Using E=QV)
The small e simply stands for the charge of an electron. When you see a small “e” this is what it will mean!

15. Learning Intentions
State that work, W, is done when a charge, Q, is moved in an electric field.
State that the potential difference (V) between two points is a measure of the work done in moving one coulomb of charge between the two points
State that if one joule of work is done moving one coulomb of charge between two points, the potential difference between the points is one volt.
State the relationship V = W/Q.
Carry out calculations involving the relationship V = W/Q
Calculate the speed of a charged particle accelerated in an electric field using the relationship QV = ½ mv2.

16. Quiz – No notes! Name a lepton Name a particle made up of 3 quarks
What’s another name for a particle made up of 3 quarks?
What’s a meson made up of?
Name a boson.
Name the force associated with this boson?
What forces in the nucleus are balanced?
What’s the defintion of 1 volt?
What’s the equation for work done in an electric field?
What equation would you use to work out the velocity of a particle as it travels through an electric field?

17. Answers