Simulation · Physics · Class 12
Two conducting spheres joined by a wire
From the lesson Electrostatics of conductors in Electrostatic Potential and Capacitance. Change the values and watch what happens.
Two conducting spheres joined by a wirePhysics · Class 12
The idea behind it
NCERT §2.9
- Metals have free electrons that can move inside the metal but cannot leave it. In a field they drift opposite to the field until the field inside falls to zero.
- In the static state the electric field inside a conductor is zero everywhere, whether it is neutral or charged and whatever the outside field.
- Just outside a charged conductor the field is normal to the surface at each point; a component along the surface would push the surface charges.
- A conductor can hold no excess charge in its interior; Gauss's law on any small closed surface inside gives zero enclosed charge, so all excess charge sits on the surface.
- The whole conductor, inside and on its surface, is at one potential. Different conductors in a system can be at different potentials.
- Field just outside a charged conductor: E = (σ/ε₀) n̂, where σ is the local surface charge density and n̂ the outward normal (inward for σ < 0).
- Electrostatic shielding: a cavity inside a conductor, with no charge in it, has zero field whatever the charges and fields outside. This protects sensitive instruments.
- Shielding works only one way: a charge placed inside a cavity still produces a field outside the conductor.
- Everyday cases: aircraft tyres made slightly conducting and fuel tankers trailing metal chains let friction charge drain to earth before it can spark.