During electrical storms if you are driving a car, it is best to stay inside the car as its metal body acts as a Faraday cage with zero electrical field inside. If in the vicinity of a lightning strike, its effect is felt on the outside of the car and the inside is unaffected, provided you remain totally inside. This is also true if an active (“hot”) electrical wire was broken (in a storm or an accident) and fell on your car.
Test prep for ap courses
An electric field due to a positively charged spherical conductor is shown above. Where will the electric field be weakest?
- Point A
- Point B
- Point C
- Same at all points
(c)
The electric field created by two parallel metal plates is shown above. Where will the electric field be strongest?
- Point A
- Point B
- Point C
- Same at all points
Suppose that the electric field experienced due to a positively charged small spherical conductor at a certain distance is E . What will be the percentage change in electric field experienced at thrice the distance if the charge on the conductor is doubled?
decrease by 77.78%.
The classic Millikan oil drop experiment setup is shown above. In this experiment oil drops are suspended in a vertical electric field against the gravitational force to measure their charge. If the mass of a negatively charged drop suspended in an electric field of 1.18×10 −4 N/C strength is 3.85×10 −21 g, find the number of excess electrons in the drop.
Section summary
- A conductor allows free charges to move about within it.
- The electrical forces around a conductor will cause free charges to move around inside the conductor until static equilibrium is reached.
- Any excess charge will collect along the surface of a conductor.
- Conductors with sharp corners or points will collect more charge at those points.
- A lightning rod is a conductor with sharply pointed ends that collect excess charge on the building caused by an electrical storm and allow it to dissipate back into the air.
- Electrical storms result when the electrical field of Earth's surface in certain locations becomes more strongly charged, due to changes in the insulating effect of the air.
- A Faraday cage acts like a shield around an object, preventing electric charge from penetrating inside.