Electric Fields | OCR A-Level Physics A (H556)
Electric Fields
- 56 questions
- 5 subtopics
- Module 6: Particles and medical physics
- Paper 2 and Paper 3
The electric field: Coulomb's law and field strength, the uniform field between parallel plates, and electric potential and potential energy..
It covers electric fields and field lines, coulomb's law and electric field strength, uniform fields, parallel plates and permittivity, electric potential and electric potential energy and capacitance of a sphere.
Sample questions from Electric Fields
Answer each one closed book first, then open the answer.
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Electric fields and field lines
What do electric field lines represent and in which direction do they point?
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Electric field lines map electric fields and show the direction of force that would act on a positive test charge. -
Electric fields and field lines
What mathematical relationship do both gravitational and electric fields from point sources share?
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Both follow an inverse square law for field strength. -
Coulomb's law and electric field strength
Write the equation for Coulomb's law and define each term.
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F = Qq/(4πε₀r²), where F is the electrostatic force, Q and q are the two point charges, ε₀ is the permittivity of free space, and r is the separation between the charges. -
Coulomb's law and electric field strength
What is the value of the permittivity of free space?
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8.85 × 10⁻¹² F m⁻¹. -
Uniform fields, parallel plates and permittivity
Write the equation for the capacitance of a parallel plate capacitor with a vacuum between the plates.
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C = ε₀A/d, where C is capacitance, ε₀ is the permittivity of free space, A is the plate area, and d is the plate separation. -
Uniform fields, parallel plates and permittivity
Calculate the capacitance when relative permittivity = 4.5, plate area = 0.08 m², plate separation = 0.0074 m.
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Capacitance = 8.85 × 10⁻¹² × 4.5 × 0.08 ÷ 0.0074 = 4.31 × 10⁻¹⁰ F. -
Electric potential
Write the equation for electric potential at distance r from a point charge Q and identify each term.
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V = Q/(4πε₀r), where V is electric potential, Q is the point charge, ε₀ is the permittivity of free space, and r is the distance from the charge. -
Electric potential
How is the change in electric potential between two points near a point charge calculated?
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Find the potential at each point using V = Q/(4πε₀r) and subtract one from the other, so ΔV = Q/(4πε₀) × (1/r₂ − 1/r₁).
The 5 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Electric fields and field lines | Recall questions on what produces electric fields, field lines, modelling a charged sphere as a point charge, defining electric field strength, and comparing gravitational and electrostatic forces. | 8 |
| Coulomb's law and electric field strength | Recall questions on Coulomb's law and force calculations, the permittivity of free space, electric field strength of a point charge and its calculation, and comparing Coulomb's law with Newton's law of gravitation. | 16 |
| Uniform fields, parallel plates and permittivity | Recall questions on uniform field strength E = V/d with calculations, capacitance of a parallel plate capacitor, relative permittivity, and the motion of charged particles in a uniform electric field. | 12 |
| Electric potential | Recall questions on electric potential and where it is zero, potential near a point charge with calculations, change in potential between two points, and the work done moving a charge in a field. | 9 |
| Electric potential energy and capacitance of a sphere | Recall questions on electric potential energy of a charge near a point charge with calculations, deriving and calculating the capacitance of an isolated sphere, and the area under a force-distance graph. | 11 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics A Active Recall Guide
Every topic, not just this one. 1,862 questions with their answers.