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Electricity 1 ELECTRICITY comes from the electrons in an atom. Electrons Negative Charge ++ 2 Electricity Static Electricity Build-up of electrical charge Electrical Current Flow of electricity through wires 3 Electricity exists naturally in nature… Static Electricity For example: Lightning Zap! ++ + + + + 4 Electric Charge The source of static in lightning and shocks is electric charge. + + + + + + - - Most objects tend to be - - 5 Net Charge of Objects: Neutral Object Charged Object -8 -6 +8 Net Charge: 0 +10 Net Charge: +4 6 Opposites Attract + - Same Charges Repel + + + + - - - 7 How do balloons stick to walls? + + - -+ - 1. Rub a balloon on a sweater to “charge it up.” 2. Negative charges in the wall repel from the balloon. - 3. The balloon sticks because the positive charges left over are attracted to the balloon. 8 The Electroscope Metal rod Electricity can move down the metal rod to the two gold leaves. 2 Gold “leaves” 9 The Electroscope When a rubber comb with a build-up of static electricity is touched to the rod... - - …the electric charge travels down the rod AND... ...builds up on both sides of the gold strip. Since the charge of the leaves are both negative the two sides of the strip repel one another. - - 10 A battery uses chemical energy to move electrical charges. 11 + Circuits flow in a circular path 12 Measurement of energy IF = 1.5 volts ?V 3.0V 1.5V 13 Voltage The unit for voltage is volts (V) and is a measure of “potential difference.” Potential Energy (height) 1.5 V Potential Difference 1.5 Meters 0.0 V To Lower Energy The potential difference (voltage) is 1.5 V. 14 Voltage The higher the energy, the greater the voltage (potential difference). 3.0 V Higher Potential energy (height) Greater Potential Difference 3.0 Meters 0.0 V To Lower Energy The potential difference (voltage) is 3.0 V. 15 Current is the rate of the flow of an electrical charge. How fast (speed) is the electricity flowing through these wires? The rate that the electricity flows is called CURRENT CURRENT is measured in AMPS (I). How fast is this water coming out? + 16 TYPES of CURRENT Direct Current (DC) flows in one direction. Alternating Current (AC) flows back and forth. 17 RESISTANCE Which of the pipes below would allow water out faster? The smaller pipe would have more resistance to the flow. 18 Resistance is measured in ohms. 19 to Electrical Current Which of the following do you think would be most resistant to electrical current? Plastic Glas s Rubber 20 These materials allow electrical charge (current) to move easily through them. They have little resistance to the flow of electrical current. They are 21 Glass Plastic Rubber These materials do not allow electrical charges (current) to move easily through them. They have a strong resistance to the flow of electrical current. They are 22 Conductors and Insulators: • Conductors allow charges to flow easily. – Examples include copper, silver, and aluminum. • Insulators do not allow charges to flow easily – Examples include glass, plastic, and rubber Rubber insulation Copper Wire 23 Wires carry an electrical charge. Copper wire covered in rubber insulation The “human” wiring system: The neuron (nerve cell) Insulation (Myelin Sheath, fatty tissue) Wires (nerve fibers) 24 Match the word on the left to the phrase on the right. Resistance Ohms How Fast? or R Current How much? AMPS (I) Voltage Volts (V) How much is it slowed down? 25 We can use this formula to figure out volts, current (amps) and resistance. 26 Calculate the potential difference (volts) across a 3 resistor if a 0.5 A current is flowing through it. V=Ix What do you know? V=? I = 0.5 A V = 0.5 A x 3 1.5 V = V =3 27 A radio with a resistance of 240 is plugged into a 120 V outlet. What is the current flowing from the outlet? V=Ix What do you know? V = 120 V I= ? = 240 1 120 V = I x 240 240 240 0.5 amps = I or V/ 28