Summary
Summary OCR-A A2 Level Electric Fields Notes
A summary of electric fields, Chapter 22 of the OCR Physics A textbook
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Seller
Follow
Content preview
Electric FieldsElectric field strength
● Protons and electrons are charged particles
○ Both create electric fields and so affect each other
● The electric field strength of an electric field at a point in
space is defined as the force experienced per unit positive
charge at that point
● Electric field strength E is
𝐹
○ E= 𝑄
where F is the force experienced by the positive
charge Q
○ The SI unit for electric field strength is NC-1
● Electric field strength is a vector quantity
○ The direction of the electric field at a point is the
direction in which a positive charge would move
when placed at that point
● Electric fields point away from positive charges and towards
negative charges
● Electric field lines map electric field patterns
○ The arrow on an electric field shows the direction of
the field
○ Electric field lines are always at right angles to the
surface of a conductor
○ Equally spaced, parallel electric field lines represent a
uniform field - the electric field strength is the same
everywhere
○ Closer electric field lines represent greater electric
field strength
● The electrical field is radial in both cases
○ The field strength decreases with distance from the
center
○ You can model the uniformly charged sphere as point
charge at its center
Coulomb’s Law
● Any 2 point charges exert an electrostatic force on each other that is directly
proportional to the product of their charges and inversely proportional to the
square of the distance between them
, ● Q and q are the magnitudes of the charges (Fig.2)
● The electrostatic force experienced by each point charge is F
● The point charges interact, and according to Newton’s 3rd Law, will exert equal but
opposite forces on each others
● From Coulomb’s Law we have:
1
○ F ∝ Qq and F ∝ 𝑟2
● We can write this using the equation where k is the constant of
proportionality
○ This constant can be written in terms of the permittivity of free space 𝜺0
○ 𝜺0 is equal to 8.85 x 10-12 Fm-1
○
● The equation for Coulomb’s Law, which can be applied to any point charges, is
○
Radial fields
● A sphere produces a radial field and the
separation between 2 adjacent electric field
lines increases with the distance from the
center of the sphere
○ The electric field strength decreases
as you move further away from the
center of the sphere
● The electric field E at a distance r from the
center of the sphere is equal to the force
experienced by a positive ‘test’ charge divided
by the charge q on the test charge
○ Therefore,
● The electric field strength is thus directly proportional to the charge Q and obeys
an inverse square law with distance r
● Point masses and point charges both produce radial fields
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller annawoodbridge. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £4.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52510 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now