Edexcel A Level (IAL) Physics-5.35 Comparing Electric & Gravitational Fields- Study Notes- New Syllabus
Edexcel A Level (IAL) Physics -5.35 Comparing Electric & Gravitational Fields- Study Notes- New syllabus
Edexcel A Level (IAL) Physics -5.35 Comparing Electric & Gravitational Fields- Study Notes -Edexcel A level Physics – per latest Syllabus.
Key Concepts:
Comparison of Electric Fields and Gravitational Fields
Electric fields and gravitational fields are both examples of force fields. They share several similarities but also have important differences.
Similarities Between Electric and Gravitational Fields
- Both are regions of space where a force acts on an object.
- Both act at a distance (non-contact forces).
- Both can be represented using field lines.
- Both follow inverse-square laws.
Inverse-square relationships:
Gravitational force: \( F = \dfrac{G m_1 m_2}{r^2} \)
Electric force: \( F = \dfrac{k q_1 q_2}{r^2} \)
Gravitational Fields
A gravitational field is produced by mass.
- Acts on masses.
- Force is always attractive.
- Field strength is given by:
\( g = \dfrac{F}{m} \)
Key properties:
- All masses attract each other.
- Gravitational fields are relatively weak.
- Field lines always point towards the mass.
Electric Fields
An electric field is produced by electric charge.
- Acts on electric charges.
- Forces can be attractive or repulsive.
- Field strength is given by:
\( E = \dfrac{F}{q} \)
Key properties:
- Like charges repel, unlike charges attract.
- Electric fields are much stronger than gravitational fields.
- Field lines point away from positive charges and towards negative charges.
Key Differences Between the Two Fields
- Gravitational fields act on mass; electric fields act on charge.
- Gravitational force is always attractive.
- Electric force can be attractive or repulsive.
- Electric fields are significantly stronger than gravitational fields.
- Mass has only one type; charge has positive and negative types.
Field Line Comparison
- Gravitational field lines always point inward.
- Electric field lines can point inward or outward.
- Closer field lines indicate a stronger field in both cases.
Energy Concepts
- Gravitational potential is always negative.
- Electric potential can be positive or negative.
- Both potentials are defined relative to infinity.
Exam Tips
- Clearly state whether attraction or repulsion is possible.
- Mention inverse-square behaviour.
- Compare mass vs charge explicitly.
- Do not confuse field strength definitions.
Example (Easy)
State one similarity between gravitational and electric fields.
▶️ Answer / Explanation
Both are regions of space where a force acts on an object.
Example (Medium)
Why can electric forces be repulsive but gravitational forces cannot?
▶️ Answer / Explanation
- Electric charge has two types.
- Like charges repel.
- Mass has only one type, so gravity is always attractive.
Example (Hard)
Explain why gravitational effects are negligible between electrons.
▶️ Answer / Explanation
- Electrons have very small mass.
- Gravitational force is extremely weak.
- Electric force dominates at atomic scales.