Physics SL

Chapters

329

Notes

Theme A - Space, Time & Motion

Theme B - The Particulate Nature Of Matter

Theme C - Wave Behaviour

Theme D - Fields

Theme E - Nuclear & Quantum Physics

Physics SL

Theme D - Fields

Unraveling Electric Fields: Inside & Outside Conducting Spheres

655 words

4 mins read

Last edited on 5th Nov 2024

A conducting sphere, be it hollow or solid, has equally spaced free electrons on its surface.
The field lines at the surface of the sphere are at a 90° angle to it.
As a result, the field is radial, similar to the field of an isolated point charge.
Real-world Example: Think of this as a sun (the sphere) with its rays (the field lines) shining radially outwards.
For any test charge outside the sphere, the field appears the same as that of a single point charge.
Fun Fact: The sphere's electric field behaves like it's coming from a tiny point at the sphere's center! Imagine a giant beach ball acting as if it were a tiny ping pong ball.

Intriguingly, there is no electric field inside a conducting sphere, whether hollow or solid.
Historical Highlight: Benjamin Franklin found this out experimentally. Remember the kite and lightning experiment? That's him!
This absence of electric field is because all the surplus charge is on the sphere's outside. Why? Because charges want to:
- Stay as far away from each other as possible.
- All be in equilibrium. (Imagine a group of people trying not to crowd each other – everyone finds a comfy spot!)
If you were to put a positive test charge (q) inside this sphere
- Forces due to the charge on the sphere's surface will cancel out.
- Therefore, no net force affects the test charge inside the sphere.
- No net force means no electric field. So, it's a total chill zone for electric fields inside the sphere!

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Physics SL

655 words

4 mins read

Last edited on 5th Nov 2024

A conducting sphere, be it hollow or solid, has equally spaced free electrons on its surface.
The field lines at the surface of the sphere are at a 90° angle to it.
As a result, the field is radial, similar to the field of an isolated point charge.
Real-world Example: Think of this as a sun (the sphere) with its rays (the field lines) shining radially outwards.
For any test charge outside the sphere, the field appears the same as that of a single point charge.
Fun Fact: The sphere's electric field behaves like it's coming from a tiny point at the sphere's center! Imagine a giant beach ball acting as if it were a tiny ping pong ball.

Intriguingly, there is no electric field inside a conducting sphere, whether hollow or solid.
Historical Highlight: Benjamin Franklin found this out experimentally. Remember the kite and lightning experiment? That's him!
This absence of electric field is because all the surplus charge is on the sphere's outside. Why? Because charges want to:
- Stay as far away from each other as possible.
- All be in equilibrium. (Imagine a group of people trying not to crowd each other – everyone finds a comfy spot!)
If you were to put a positive test charge (q) inside this sphere
- Forces due to the charge on the sphere's surface will cancel out.
- Therefore, no net force affects the test charge inside the sphere.
- No net force means no electric field. So, it's a total chill zone for electric fields inside the sphere!

Dive deeper and gain exclusive access to premium files of Physics SL. Subscribe now and get closer to that 45 🌟

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