Reading Time: 2 minutesElectric Field Strength (
Electric Potential (
Electric Fields: Understanding Force, Field Strength, and Potential in A-Level Science
What Are Electric Fields?
An electric field is a region around a charged object where other charges experience a force.
Key Concepts in Electric Fields
Coulomb’s Law
The force (
) between two point charges:
![\[ F = k \frac{q_1q_2}{r^2} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-4d64994e77dfed61973bf9e6ebb89402_l3.png "Rendered by QuickLaTeX.com")
Where:
: Coulomb constant.
: Charges (
).
: Distance between charges (
).
: Coulomb constant.
: Charges (
).
: Distance between charges (
).Electric Field Strength (
)
The force per unit charge in an electric field:
![\[ E = \frac{F}{q} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-6451b458fc538ef84129b9dc02ba789d_l3.png "Rendered by QuickLaTeX.com")
Or for a point charge:
![\[ E = k \frac{Q}{r^2} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-8cb467e42b5740d0aa6a196afd355eab_l3.png "Rendered by QuickLaTeX.com")
Where 
is measured in 
.
Electric Potential ()
)The work done per unit charge in bringing a charge from infinity to a point:
![\[ V = k \frac{Q}{r} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-79efb3bfd90d80073ce237ae80ba45fa_l3.png "Rendered by QuickLaTeX.com")
Applications of Electric Fields
Capacitors
Store electrical energy in electric fields.
Particle Accelerators
Use electric fields to accelerate charged particles.
Medical Imaging
Electrostatics is used in devices like X-ray tubes.
Example Problem
Find the electric field strength at a distance of 
from a charge of 
.
- Formula:
- Substitute Values:
![\[ E = 8.99 \times 10^9 \cdot \frac{2}{0.5^2} = 7.192 \times 10^{10} \, \text{N/C} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-083001fa7d146cb388adc588d0606a77_l3.png "Rendered by QuickLaTeX.com")
Common Mistakes in Electric Field Calculations
- Forgetting to square the distance (
). - Mixing up force () and field strength ().
- Ignoring the sign of charges in calculations.
).Practice Questions
- Calculate the force between two charges (
) separated by 
. - Explain the difference between electric field strength and electric potential.
- Describe one real-world application of electric fields in medical devices.
) separated by 
.
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