Lesson 10
Review
Review the topic after the test and consolidate remaining weak areas.
Objectives
Lesson outcomes
- Use test feedback to correct errors in magnetic fields and induction.
- Improve written explanations for Hall effect and induction questions.
- Choose targeted follow-up practice for remaining weak B4 skills.
Syllabus
CIE 9702 syllabus points
19 linked
- 20.1.1 understand that a magnetic field is an example of a field of force produced either by moving charges or by permanent magnets
- 20.1.2 represent a magnetic field by field lines
- 20.2.1 understand that a force might act on a current-carrying conductor placed in a magnetic field
- 20.2.2 recall and use the equation F = BIL sin θ, with directions as interpreted by Fleming’s left-hand rule
- 20.2.3 define magnetic flux density as the force acting per unit current per unit length on a wire placed at right‑angles to the magnetic field
- 20.3.1 determine the direction of the force on a charge moving in a magnetic field
- 20.3.2 recall and use F = BQv sin θ
- 20.3.3 understand the origin of the Hall voltage and derive and use the expression VH = BI / (ntq), where t = thickness
- 20.3.4 understand the use of a Hall probe to measure magnetic flux density
- 20.3.5 describe the motion of a charged particle moving in a uniform magnetic field perpendicular to the direction of motion of the particle
- 20.3.6 explain how electric and magnetic fields can be used in velocity selection
- 20.4.1 sketch magnetic field patterns due to the currents in a long straight wire, a flat circular coil and a long solenoid
- 20.4.2 understand that the magnetic field due to the current in a solenoid is increased by a ferrous core
- 20.4.3 explain the origin of the forces between current-carrying conductors and determine the direction of the forces
- 20.5.1 define magnetic flux as the product of the magnetic flux density and the cross-sectional area perpendicular to the direction of the magnetic flux density
- 20.5.2 recall and use Φ = BA
- 20.5.3 understand and use the concept of magnetic flux linkage
- 20.5.4 understand and explain experiments that demonstrate: • that a changing magnetic flux can induce an e.m.f. in a circuit • that the induced e.m.f. is in such a direction as to oppose the change producing it • the factors affecting the magnitude of the induced e.m.f.
- 20.5.5 recall and use Faraday’s and Lenz’s laws of electromagnetic induction
Definitions
Required definitions
Magnetic flux density
the force acting per unit current per unit length on a wire placed at right angles to the magnetic field.
Magnetic flux
magnetic flux density multiplied by the cross-sectional area perpendicular to the field.
Lesson Notes
Student guidance and lesson notes
Overview
This review lesson uses the B4 test to consolidate remaining weak areas. The priority is to turn each mistake into a specific correction strategy.
What You Need to Know
- Magnetic fields questions often fail because the equation is right but the direction or geometry is wrong.
- Hall effect explanations need a clear sequence: moving charges, magnetic force, charge separation, Hall voltage.
- Induction explanations need a clear sequence: changing flux linkage, induced e.m.f., induced current if the circuit is complete, opposition by Lenz’s law.
- Corrections should include improved diagrams or written statements, not only final numerical answers.
How to Work Through It
- Sort your test errors by topic and by skill type.
- Rewrite one calculation response with full working and units.
- Rewrite one explanation response using precise cause-and-effect language.
- Choose follow-up questions that target your weakest category.
Check Your Understanding
- Can you explain why your original incorrect answer was tempting?
- Can you write a corrected induction explanation without using vague phrases?
- Can you identify the diagram feature that controls the force or induced current direction?
- Can you choose the next question type that will improve your weakest area?
Common Mistakes
- Copying the mark scheme without understanding the physics step that was missing.
- Correcting only numerical answers and leaving unclear diagrams unchanged.
- Revising the whole topic equally instead of targeting the error pattern.
- Treating Lenz’s law and Fleming’s left-hand rule as interchangeable.
Next Steps
- Add your corrected B4 targets to the wider A Level revision list.
- Revisit the original lesson pages for any skill that remains insecure.