1. Moving Electricity If charges in a conductor (like a metal) are connected to a battery or source of electric potential difference, they will move.

2. Electric Current Current is the movement or flow of charges. Current is the movement or flow of charges. Current = I = charges/time = coulombs/sec = amps Current = I = charges/time = coulombs/sec = amps 1 Amp of current is a lot of current (relatively speaking) 1 Amp of current is a lot of current (relatively speaking)

3. Electric Current & People Range of current and its affects on humans Range of current and its affects on humans 1 mA (.001A) Slight tingling 1 mA (.001A) Slight tingling 5 mA (.005A) Slight shock, disturbing 5 mA (.005A) Slight shock, disturbing 6-30 mA painful shock, muscle control lost 6-30 mA painful shock, muscle control lost 50-150 mA Extreme pain, resp. arrest. Death possible 50-150 mA Extreme pain, resp. arrest. Death possible 1000-4300 mA Death likely, rhythmic pumping of heart ceases 1000-4300 mA Death likely, rhythmic pumping of heart ceases The good thing is our bodies have a lot of resistance (100,000 ohms – ish) so we have lots of resistance to current flow (but, our resistance goes down if we’re wet or wearing copper clothing) The good thing is our bodies have a lot of resistance (100,000 ohms – ish) so we have lots of resistance to current flow (but, our resistance goes down if we’re wet or wearing copper clothing)

4. Ohm’s Law: resistance & resistors To produce a current a “difference in potential” is required (voltage). To produce a current a “difference in potential” is required (voltage). The Current (I) which flows in a conductor is proportional to this Voltage (V). The Current (I) which flows in a conductor is proportional to this Voltage (V). The Resistance of the circuit also influences the flow of charge. The Resistance of the circuit also influences the flow of charge. Ohm’s Law: V = I R Ohm’s Law: V = I R R = resistance = ohms Ω R = resistance = ohms Ω

5. Resistors Resistors resist the flow of current. Resistors resist the flow of current. Resistors are used in circuits to control or regulate the amount of current Resistors are used in circuits to control or regulate the amount of current Many simple electrical devices are simple resistors, examples include hot glue guns, waffle irons, clothes irons, toasters. Many simple electrical devices are simple resistors, examples include hot glue guns, waffle irons, clothes irons, toasters. In these examples resistors heat up as they absorb energy provided by the moving charges. In these examples resistors heat up as they absorb energy provided by the moving charges.

6. Resistivity The resistance of a material depends on its geometry and the type of material its made of. The resistance of a material depends on its geometry and the type of material its made of. Resistivity is a property of a material which tells you how much it resists current flow. The symbol is ρ. Resistivity is a property of a material which tells you how much it resists current flow. The symbol is ρ. R (resistance) = ρL/A where L = length of the conductor and A is the cross-sectional area. R (resistance) = ρL/A where L = length of the conductor and A is the cross-sectional area.

7. Resistivity MaterialResistivity Copper1.68 x 10 -8 Gold2.44 x 10 -8 Iron9.71 x 10 -8 Waffle812 x 10 8

8. Electric Power Watt?, not another electricity topic Watt?, not another electricity topic Electric Power = energy used per time Electric Power = energy used per time P = J/sec = ? (yes) P = J/sec = ? (yes) For electricity, P = VI = I 2 R = V 2 /R For electricity, P = VI = I 2 R = V 2 /R Many electrical devices are rated by their power usage. For example, a 100W bulb uses 100 joules/sec. Many electrical devices are rated by their power usage. For example, a 100W bulb uses 100 joules/sec.