Electrical principles and technologies Section 1.1

The Plan Quick lab Discuss static electricity and electrical discharge Demo Lab I can explain static electricity and electrical discharge. http://blog.ssis.edu.vn/103059/2013/09/17/does-the-color-of-hair-affect-how-much-static-electricity-it-can-carry/

Quick lab (P. 273)

Static electricity Static electricity is a stationary electric charge. Understanding static electricity starts with the charges in an atom. https://www.clickenergy.com.au/about-us/news-blog/handy-facts-static-electricity/

Recall A proton is a positively charged particle in the nucleus of an atom. An electron is an invisible negatively charged particle that orbits the nucleus of an atom.

Electrical charge --+-++ --++++ ---+-+ An object that has equal amounts of positive (protons) and negative (electrons) charges is neutral. Most objects are neutral. If an object has more electrons than protons it is negatively charged. If it is stationary it is called static. ++-+-- ++++-+ --+--+ --+-++ --++++ ---+-+ Neutral Charge Positive Charge Negative Charge

How Do we get different charges? Charge separation is the concentration of like charges in specific areas of a neutral object. It is caused by: Friction The approach of a charged object

How do we know the charge of an object? We know the charge of an object by looking at the triboelectric series. It is a list that predicts what charge objects will become based on polarity (i.e., how much pull there is on electrons).

Electrical law The charges of an atom can cause either attractive or repulsive forces. Opposite charges attract each other, while like charges repel each other. A negative charge can attract a neutral charge because it ‘pushes’ other negatives away.

Not like current Static electricity does not flow like current, but can electrically discharge.

Electrical discharge Electrical discharge is the sudden transfer of electrical charge from one object to another, indicated by a spark. E.g., Getting a shock from metal after walking across the carpet.

How is lightning caused? Water droplets and ice crystals in the clouds are struck by strong winds, colliding and rubbing against each other. Creates a charge separation. Attraction to the ground charges. An electrical discharge occurs.

Van de Graaff generators (vdg) VDGs are especially effective at building up static charge by using friction. A rubber belt rubs a piece of metal and there is a transfer of electrons from the metal to the rubber band.

Demo: vdg and static charge p. 275 Confetti Taping thin paper strips Fur standing up Hair standing up? http://www.amazing1.com/products/200-000-volt-van-de-graaff-static-electricity-generator.html

Lab Explain the charges of each substance.

homework P. 278 #1-8.