Electric Charge & Static Electricity 17.1

Like charges repel one another while opposite charges are attracted to one another. Law of Electric charge--

Protons = ___ charge Neutrons = ___ charge Electrons = ___ charge WHAT ARE THE CHARGES WITHIN AN ATOM?

Because protons have a positive charge and electrons have a negative charge. They are OPPOSITES! Why are protons & electrons attracted to each other?

The attraction keeps the electrons from flying away from the nucleus. Why is it important that the electrons and protons are attracted to each other?

Electric Force—force between two charged objects

The region around a charged object where a force is exerted on other objects size of the field depends on 1.amount of charge 2.distance between the charges Electric Field

- charge = gained electrons + charge = lost electrons If atoms have equal numbers of protons & electrons how do they become charged?

OBJECTS BECOME CHARGED BY FRICTION, CONDUCTION, & INDUCTION.

Movement of charged particles when objects have contact and slide across one another Friction

Movement of charged particles when objects come in direct contact. Conduction

when charges in an uncharged metal object are rearranged w/out direct contact w/the charged object. Induction

No charges are created or destroyed, they simply move from one atom to another. Conservation of Charge

When an electro-scope is charged, the metal leaves have the same charge and repel each other.

A material in which charges can move freely Conductors

A material in which charges CANNOT move freely. Insulators

- Electric charge at rest - Generally produced by friction or induction Example—clothes sticking together, Hair standing up when rubbed on a balloon Static Electricity

The release of electricity stored in a source; ex.—lightning Electric Discharge

John Travolta Balloons and Static Electricity

17.2

The rate at which charges pass a given point Expressed in amperes (amps) Electric Current Electrons moving in a wire make up current and provide energy to the things that you use each day.

AC = alternating current Current from outlets Charges shift from flowing in one direction to flowing in the reverse direction In the US most appliances are made to 120 V AC

DC = direct current Current from batteries Always flows in the same direction DC

The amount of energy released as a charge moves between two points in the path of a circuit Expressed in volts = V The higher the voltage is, the more energy is released per charge Voltage

Batteries are made with various voltages for use in many different devices.

Electrical friction Expressed in ohms (Ώ) or R (equations) the higher the resistance is, the lower the current Resistance

Depends on the object’s material, thickness, length, & temp.

Good conductors have lower resistance, ex., Cu Poor conductors have higher resistance, ex., Fe Resistance

- can repel magnets Superconductors One interesting property of superconductors is that they repel magnets. The superconductor in this photo is repelling the magnet so strongly that the magnet is floating.

Cells- change chemical or radiant energy into electrical energy (batteries are cells too) Generating Electrical Energy

This cell uses the juice of a lemon as an electrolyte and uses strips of zinc and copper as electrodes. Convert chemical energy into electrical energy

Convert thermal energy into electrical energy Thermocouples In a simple thermocouple, one section of the loop is heated and one section is cooled.

Light energy converted into electrical energy Solar energy is converted with this Photocell

17.4 Circuits

1.Energy source 2.Wires 3.Load Parts of a Circuit

closed opened SWITCHES

1. SERIES: all parts are connected in a single loop if one part stops working—it all stops; bulbs get dimmer as more bulbs are added Uses: burglar alarms TYPES OF CIRCUITS

2. PARALLEL loads are connected side by side; charges have more than one path to follow; loads use the same voltage USES: Christmas tree lights, house wiring CIRCUITS

CAUSES: 1.Broken wires 2.Water 3.Overloaded CIRCUIT FAILURE

CONTAIN A METAL STRIP THAT MELTS WHEN CURRENT GETS TOO HIGH FUSES

Metal in breaker warms, bends, opens switch, stops flow of current GFCI (ground fault circuit interrupter)- if the current on either side of the outlet differs the charges stop flowing CIRCUIT BREAKERS

1.Make sure the insulation on cords is not worn 2.Do not overload circuits by plugging in too many electrical devices 3.Do not use electrical devices while your hands are wet or while you are standing in water 4.Never put objects other than a plug into electrical outlet ELECTRICAL SAFETY TIPS