Distribution of Charge Electroscope Spherical vs. Irregular shaped objects Lightning and Lightning rods

The Electroscope A device that can be used to detect the presence of a nearby electrostatic charge Diagram:

The Electroscope The electroscope can be charge by contact or by induction Diagram of Charging by induction: Step 1: Step 2: grounding Step 3:

Distribution of Charge Three Rules to determine the location of charges Charge is EVENLY DISTRIBUTED over the surface of a conducting sphere Like charges repel, and want to get as far away from each other as possible! If charging by contact, the charged objects will have identical charge if the objects are identical. Otherwise, all we can be certain of is that the charge TYPE (- or +) will be the same. Charge is ONLY found on the outside of a conductor—there is no charge on the inside of a conducting material

Distribution of Charge

Distribution of Charge Three Rules to determine the location of charges For irregular shaped conductors, the charge accumulates in regions of greatest curvature For example, the sharpest point on an object will collect the most charge

Lightning! Thunderstorms typically involve large storm clouds that have strong updrafts and downdrafts These up and down wind currents carry rain drops and hailstones up and down within the cloud Collisions between all the hailstones, etc. cause the ionization of particles in the clouds…For some reason, the negative charges tend to collect near the bottom of the cloud

Lightning! The strong negative charges in the cloud induces positive charges in the ground below the cloud: When the charge builds up enough, the cloud will discharge in one of three ways, depending on what the closest &/or easiest discharge path is:

Lightning! Cloud to ground: Discharge between the bottom of the cloud and the closest and/or most positively charged point on the ground - typically a pointed object, like a tree, a steeple, TV antenna, etc. In-Cloud: Discharge occurring between the top and the bottom of the cloud Cloud-to-Cloud: Discharge between the negative charges in one cloud and the positive charges in another nearby cloud

Lightning Rods Invented in the 1700’s in order to protect homes/barns/churches, etc. from lightning strikes Lightning is “attracted” to tall pointed objects. If this happens to be the top of a house, then the electricity will go through the house to get to the ground…typically starting a fire Lightning rods are designed to attract the lightning strikes The lightning rods are made of pointed metal (like copper, which is a great conductor) that is placed above the highest point on a building The rod is connected with a strong conducting wire to a metal stake or plate, typically buried deep in the ground