Physics 2

Electricity Section 1 Transfer of Electric Charge 〉 Protons and neutrons are relatively fixed in the nucleus of the atom, unlike electrons that can easily move form one atom to another. 〉When different materials are rubbed together, electrons can be transferred from one material to the other. • The direction in which the electrons are transferred depends on the materials. Electricity Section 1 Transfer of Electric Charge Electricity Section 1 Visual Concept: Electrical Conductors and Insulators Electricity Section 1 Transfer of Electric Charge, continued • Conductors allow charges to flow; insulators do not. – electrical conductor: a material in which charges can move freely – electrical insulator: a material in which charges cannot move freely • Charges can move within uncharged objects. – The charges in a neutral conductor can be redistributed without changing the overall charge of the object. – Although the total charge on the conductor will be zero, the opposite sides can have an induced charge. Electricity Section 1 Induced Charges A negatively charged rod brought near a metal doorknob induces a positive charge on the side of the doorknob closest to the rod and a negative charge on the side farthest from the rod. Electricity Section 1 Charging by Contact When a negative rod touches a neutral doorknob, electrons move from the rod to the doorknob. The transfer of electrons to the metal doorknob gives the doorknob a net negative charge. Electricity Section 1 Visual Concept: Charging by Contact Electricity Section 1 Transfer of Electric Charge, continued • Objects can be charged by contact. – The transfer of electrons from one object to another can charge objects. – Objects charged by touching a charged object to a neutral object are said to be charged by contact. • Objects can be charged by friction. – Charging by friction occurs when one material gains electrons and becomes negatively charged, and the other loses electrons and becomes positively charged. – Your clothes are charged by friction as they rub against each other inside the dryer, and stick together because of static electricity. Electricity Section 1 Transfer of Electric Charge, continued • A surface charge can be induced on insulators. – When a charged object is brought near an insulator, the positions of the electrons within the individual molecules of the insulator change slightly. – One side of a molecule will be slightly more positive or negative than the other side. • The molecules are polarized.