Sci I - Conductors and Insulators

What are the two contexts in which a substance can be a good conductor?

Heat and electricity.

What makes a substance a good conductor of heat?

Its ability to quickly exchange heat energy with its surroundings.

What makes a substance a good conductor of electricity?

Its ability to easily allow charge to flow through it.

Why are good conductors effective for both heat and electricity?

Because their outer electrons are very loosely bound and can move freely between atoms.

Which materials are generally good conductors?

Metals such as aluminum and copper.

Why are metals good conductors?

They are in the middle columns of the periodic table with unfilled outer orbital shells, allowing electron movement.

Which materials act as insulators?

Plastics and rubber.

Why are electric wires coated with plastic?

To insulate and protect us from electric charge while the copper inside conducts.

What does a conducting wire allow even if it has no net electric charge?

Charges to flow freely through it.

What happens when a conductor gains a net electric charge?

The charges spread out to minimize repulsion.

What analogy explains how charges distribute on a conductor?

People in a circular room spread out equally along the wall to be as far apart as possible.

Where do extra electrons on a metal sphere end up?

On the surface of the sphere, equally spaced apart.

What happens to an electron placed at the center of a charged metal sphere?

It feels equal repulsion in all directions, so the net force is zero.

What is the net electric field at the center of a charged conductor?

Zero.

What is the electric field everywhere inside a charged spherical conductor?

Zero, due to cancellation of forces.

What is the general rule for the inside of a charged conductor?

The electric field inside is always zero.

What is a Faraday cage?

A structure that shields the inside from electromagnetic radiation by distributing charges on its surface.

What is an everyday example of a Faraday cage providing safety?

A car during a thunderstorm, since its metal frame protects passengers if struck by lightning.

What household appliance is an example of a Faraday cage?

A microwave oven, which prevents signals from reaching a phone inside it.

What happens if a conductor is not spherical?

Charges still distribute to create zero electric field inside, but the pattern differs.

Why can’t a charged conductor have a non-zero electric field inside?

Because charges would keep moving until equilibrium is reached.

Where does charge tend to build up most on irregularly shaped objects?

At corners and pointed surfaces.

How does a lightning rod work?

Its pointed metal tip collects higher charge density during a storm, making it the most likely target for a lightning strike.