1. Electric Current

2. What is electrical current? When electrical charges move, they are known as electric current Electrical current is the flow of electrons through a substance (a conductor). Usually, it is the flow of electrons through wires

3. Conductors and Insulators: Conductors - materials through which charges move easily – metals (especially copper and aluminum) Insulators - materials through which charges will not move easily – glass, dry wood, most plastics, rubber, dry air

4. The two types of electrical current: Direct Current (DC) – electrons flow only in one direction (battery powered devices) Alternating Current (AC) – electrons move back and forth (plug-in outlet devices)

5. Circuits: A series of conductors moving current around is known as a circuit Circuits must have a completely closed “loop” for current to flow If there is a break in the circuit, current cannot travel

6. Batteries and DC In a DC circuit, electrons flow from negative to positive. Fan motor etc. + + + - - -

7. AC Current In circuits with alternating current (AC), the electrons move back and forth in the wires AC is produced by a generator which is sometimes far from the point of use. flow of current

8. Properties of Electrical Current: Voltage ( V ) – a measurement of the amount of force driving electrical current through a circuit Voltage is measured in volts (V) Voltage is also known as electric potential

9. Properties of Electrical Current: Current ( I ) – a measurement of the amount of electricity flowing through a circuit Current is measured in Amperes (A or Amps) more voltage  more current

10. Properties of Electrical Current: Resistance ( R ) – a measurement of how hard it is for electrical current to flow through a circuit Resistance is measured in the unit Ohms (  ) Anything in a circuit that slows current down, such as an appliance, a bulb, or an insulator is called a resistor

11. Hose Analogy: Compare water flowing through a hose to current flowing through a wire: – Voltage is the water pressure – Current is how much water flows through the hose – Resistance is anything that slows the water down (hose diameter, blockages, “kinks”) voltage resistance current

12. Ohm’s Law: I = V÷R V = I×R R = V÷I V = voltage (V) I = current (Amps) R = resistance (  )

13. Ohm’s Law Problem #1 1.A 9 volt battery is placed in a circuit with 2 ohms of resistance. How much current flows in the circuit? GivenUnkEquationSolution I = V÷R I = ?V = 9 v R = 2 Ω I = V÷R I = 9 ÷ 2 I = 4.5 A

14. Ohm’s Law Problem #2 2.A circuit with a 12V battery produces a current of 3.2 Amps. How much resistance is in the circuit? GivenUnkEquationSolution R=V÷I R=?V = 12v I = 3.2A R = V÷I R = 12 ÷ 3.2 R = 3.75 Ω

15. Ohm’s Law Problem #3 3.A circuit with 0.75  of resistance has a current of 2.0 Amps running through it. What amount of voltage is in the circuit? GivenUnkEquationSolution V=I×R V=?R=0.75 Ω I=2.0 A V = I×R V = 0.75 × 2.0 V = 1.5 v

16. Problems to solve: 1.A 9.0V battery is in a circuit with a bulb that provides 1.5  of resistance. What amount of current flows in the circuit? 2.4.0A of current flow through a circuit with 30.0  of resistance. What is the voltage of the power source? 3.A battery provides 1.5V of potential to a circuit with a motor. If the circuit draws 0.55A of current, what resistance does the motor provide?