8 Motion of a charged particle in the magnetic field

Long-term plan unit: Magnetic field

School:

Date:

Teacher name:

Grade: 10

 Number present:

Absent:

Theme of the lesson

Lorentz force. Motion of a charged particle in the magnetic field

Learning objectives that are achieved at this lesson (Subject Programme reference)

·         to investigate the effect of a magnetic field on moving charged particles;

Lesson objectives

By the end of this lesson, students will be able to:

·         Calculate the the magnetic flux density of the magnetic field;

·         Calculate the centripetal force provided by the magnetic field;

·         Calculate the speed of the charged particles;

·         Describe and analyse qualitatively the deflection of beams of charged particles by uniform electric and uniform magnetic fields;

·         Describe the effects of magnetic fields on moving charges;

·         Explain how electric and magnetic fields can be used in velocity selection;

·         Explain the main principles of one method for the determination of   and e/m_e for electrons;

Assessment criteria

Application

Calculate the the magnetic flux density of the magnetic field;

Calculate the centripetal force provided by the magnetic field;

Calculate the speed of the charged particles;

Analysis

Describe and analyse qualitatively the deflection of beams of charged particles by uniform electric and uniform magnetic fields;

Describe the effects of magnetic fields on moving charges;

Explain how electric and magnetic fields can be used in velocity selection;

Explain the main principles of one method for the determination of   and e/m_e for electrons;

Language objectives

Subject-specific vocabulary & terminology

magnetic force on a moving charge

a beam of electrons

electron gun

Fleming’s left-hand rule

deflected up the page

deflected down the page

into the page

out of page

the magnetic flux density B (strength of the magnetic field)

the charge Q on the particle

the speed v of the particle

Useful set(s) of phrases for dialogue/writing

A charged particle entering at right angles to a uniform magnetic field describes a circular path because the magnetic force is perpendicular to

the velocity.

Type of differentiation

Differentiated poster-session , Collaborative Learning, Progressive Task with Digital resources

Values instilled at the lesson

Safety, Consideration to others, Co-operation, Opportunity for Life-Long Learning, Academic Integrity and Transparency, Respect for Self and Others

Cross-curricular links

Mathematics, Chemistry

ICT skills

Research skills, use of video as introduction

Previous learning

Grade 8: magnetic fields; representation of fields by field lines; fields of permanent magnets

Grade 8: electrical equations: V = IR, P = IV

Course of the lesson

Planned stages of the lesson

Planned activities at the lesson

Resources

Beginning

(0-3 min)

(4-7 min)

Teacher:

-Introduces the topic of day and spelling out the learning outcome they will possess after the study.

1. Organizational moment to acquaint students with the

·         The theme of the lesson

·         The objectives of the lesson

·         The criteria of success for the lesson

·         The plan of events for the lesson

Motivation

•      If the speed of the particle and radius of its path are known, then the specific charge/the ratio of charge to mass can be found. Then, if the charge on the particle is known, its mass may be calculated.

•      The tracks of charged particles are made visible in a bubble chamber. Analysing these tracks gives information as to the sign of the charge on the particle and its specific charge.

Middle

8-24 min

(G) Group work.

Ask learners to divide into two  groups and research tasks: the charge-to-mass ratio of an electron and velocity selection of charged particles. The results of group works should be given in the form of presentations to be defended by learners. Assessment criteria should be agreed in advance.

GROUP 1: The charge-to-mass ratio of an electron

GROUP 2: Velocity selection of charged particles

(T) Teacher explanation.

The study of the new material is based on the explanation of the topic by the teacher accompanied by a presentation.

  25-30 min

(I) Individual work. Testyourself

This question is about the velocity selector shown

in Figure 11.3.

a State the directions of the magnetic and electric forces on a positively charged ion travelling towards the slit S.

b The speed of the ion is given by the equation: v =E/B

Calculate the speed of an ion emerging from the slit S when the magnetic flux density is 0.30 T and the electric field strength is 1.5 ∙ 10³ V m⁻¹.

c Explain why ions travelling at a speed greater than your answer to b will not emerge from the slit.

(f) Formative assessment.

A set of calculations based on the velocity selector can be used to test understanding of the underlying principles and use of equations.

Structured questions.

1.   A proton of kinetic energy 15 keV travelling at right angles to a magnetic field describes
a circle of radius of 5.0 cm. The mass of a proton is 1.7 ´ 10⁻²⁷ kg.

a    Show that the speed of the proton is 1.7 ´ 10⁶ m s⁻¹.                               [3]

b    For this proton, calculate the centripetal force provided by the magnetic field.                                                                                                    [3]

c    Determine the magnetic flux density of the magnetic field that keeps the proton moving
in its circular orbit.                                                                                [3]

d    How long does it take for the proton to complete one orbit?                     [2]

2.   The diagram shows a velocity-selector for charged ions. Ions of speed v emerge from the slit.

      The parallel plates have a separation of 2.4 cm and are connected to a 5.0 kV supply.
A magnetic field is applied at right angles to the electric field between the plates such
that the positively charged ions emerge from the slit of the velocity-selector at a speed of 6.0 ´ 10⁶ m s⁻¹. Calculate the magnetic flux density of the magnetic field.                                                                                      [6]

Ending

(38-40 min)

At the end of the lesson, learners reflect on their learning:

-           What has been learned

-           What remained unclear

-           What is necessary to work on

Where possible the learners could evaluate their own work as well as the work of their classmates using certain criteria.

Differentiation – how do you plan to give more support? How do you plan to challenge the more able learners?

Assessment – how are you planning to check students’ learning?

Health and safety regulations

·         Multiple Intelligences

-          Visual will watch the video

-          Analytical take information from the texts

·         Differentiation by questioning and dividing in group

·         Worksheet with varied difficulties

Assessment – how are you planning to check students’ learning?

The output for the worksheet will serve as assessment

Questions during the lesson will also serve as formative assessment.

Be careful when use the laser-coder

Reflection

Were the lesson objectives/learning objectives realistic? Did all learners achieve the LO?

If not, why?

Did my planned differentiation work well?

Did I stick to timings?

What changes did I make from my plan and why?

Use the space below to reflect on your lesson. Answer the most relevant questions from the box on the left about your lesson. 

Summary evaluation

What two things went really well (consider both teaching and learning)?

1:

2:

What two things would have improved the lesson (consider both teaching and learning)?

1:

2:

What have I learned from this lesson about the class or achievements/difficulties of individuals that will inform my next lesson?