Slides
Lesson slides
Slides for the lesson
Open resourceLesson 04
Practice
Consolidate electric fields and compare them with gravitational fields.
Objectives
Lesson outcomes
- Retrieve the key definitions, diagrams, and equations across electric fields.
- Practise mixed questions involving uniform fields, Coulomb's law, point-charge fields, potential, and potential energy.
- Compare electric field models with gravitational field models accurately.
- Identify which B2a electric fields skills need targeted follow-up practice.
Syllabus
CIE 9702 syllabus points
12 linked
- 18.1.1 understand that an electric field is an example of a field of force and define electric field as force per unit positive charge
- 18.1.2 recall and use F = qE for the force on a charge in an electric field
- 18.1.3 represent an electric field by means of field lines
- 18.2.1 recall and use E = ∆V / ∆d to calculate the field strength of the uniform field between charged parallel plates
- 18.2.2 describe the effect of a uniform electric field on the motion of charged particles
- 18.3.1 understand that, for a point outside a spherical conductor, the charge on the sphere may be considered to be a point charge at its centre
- 18.3.2 recall and use Coulomb’s law F = Q1Q2 / (4πε 0 r 2) for the force between two point charges in free space
- 18.4.1 recall and use E = Q / (4πε 0 r 2) for the electric field strength due to a point charge in free space
- 18.5.1 define electric potential at a point as the work done per unit positive charge in bringing a small test charge from infinity to the point
- 18.5.2 recall and use the fact that the electric field at a point is equal to the negative of potential gradient at that point
- 18.5.3 use V = Q / (4πε 0 r) for the electric potential in the field due to a point charge
- 18.5.4 understand how the concept of electric potential leads to the electric potential energy of two point charges and use EP = Qq / (4πε 0 r)
Definitions
Required definitions
Electric field
a region where a charge experiences a force; electric field strength is force per unit positive charge.
Electric potential
the work done per unit positive charge in bringing a small test charge from infinity to the point.
Lesson Notes
Student guidance and lesson notes
Overview
This lesson consolidates the B2a electric fields sequence. You should be able to choose between uniform-field, point-charge force, point-charge field, potential, and potential energy models, and compare electric fields directly with gravitational fields.
What You Need to Know
- Use electric field strength to compare the force on a positive test charge at different points.
- Uniform-field questions often use F = qE and E = delta V / delta d.
- Point-charge force questions use Coulomb’s law and require charge signs for direction.
- Point-charge field, potential, and potential energy questions use different equations with the same centre-to-centre separation.
- Electric fields can be attractive or repulsive because charge can be positive or negative.
- Electric and gravitational fields share inverse-square models, but their source quantities and force directions differ.
How to Work Through It
- Start with quick retrieval of chapter 18 definitions, diagrams, and equations.
- Work through mixed questions without sorting them by lesson first.
- Mark each response for model choice, charge signs, radius/separation, units, and explanation quality.
- Finish by writing the two electric fields skills that need the most follow-up.
Check Your Understanding
- Can you decide whether a question needs a uniform-field or point-charge model?
- Can you keep force, field strength, potential, and potential energy separate?
- Can you explain how electric fields compare with gravitational fields?
- Can you use charge signs to predict force direction and potential sign?
Common Mistakes
- Revising equations without practising when each model applies.
- Using charge values without converting prefixes into coulombs.
- Mixing up potential and potential energy.
- Forgetting that field lines show the direction of force on a positive test charge.
Next Steps
- Revisit the weakest B2a lesson page before moving into capacitors.
- Keep corrected examples available for later synoptic field questions.
Lesson Resources
Materials for this lesson
Use these videos, slide decks, documents, or links to work through the lesson.