2. Electricity Currents, Circuits

3. Electricity that moves… Current: The flow of electrons from one place to another. Current: The flow of electrons from one place to another. Measured in amperes (amps) Measured in amperes (amps) Kinetic energy Kinetic energy

4. How can we control currents? With circuits. With circuits. Circuit: is a path for the flow of electrons. We use wires. Circuit: is a path for the flow of electrons. We use wires.

5. There are 2 types of currents: Direct Current (DC) – Where electrons flow in the same direction in a wire. Direct Current (DC) – Where electrons flow in the same direction in a wire.

6. There are 2 types of currents: Alternating Current (AC) – electrons flow in different directions in a wire Alternating Current (AC) – electrons flow in different directions in a wire

7. There are 2 types of circuits: Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off. Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off.

8. Series Circuit

9. There are 2 types of circuits: Parallel Circuit – there are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off. Parallel Circuit – there are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off.

10. Parallel Circuit

11. What is Resistance? The opposition to the flow of an electric current, producing heat. The opposition to the flow of an electric current, producing heat. The greater the resistance, the less current gets through. The greater the resistance, the less current gets through. Good conductors have low resistance. Good conductors have low resistance. Measured in ohms. Measured in ohms.

12. What Influences Resistance? Material of wire – aluminum and copper have low resistance Material of wire – aluminum and copper have low resistance Thickness – the thicker the wire the lower the resistance Thickness – the thicker the wire the lower the resistance Length – shorter wire has lower resistance Length – shorter wire has lower resistance Temperature – lower temperature has lower resistance Temperature – lower temperature has lower resistance

13. What is Voltage? The measure of energy given to the charge flowing in a circuit. The measure of energy given to the charge flowing in a circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.

14. Difference b/t Volts and Amps Example – you could say that… Example – you could say that… Amps measure how much water comes out of a hose. Amps measure how much water comes out of a hose. Volts measure how hard the water comes out of a hose. Volts measure how hard the water comes out of a hose.

15. Ohm’s Law Resistance = Voltage / Current Resistance = Voltage / Current Ohms = Volts / Amps Ohms = Volts / Amps

16. Practice with Ohm’s Law OhmsVoltsAmps 410025 1515010 23015 9455 6488

17. What are batteries ? Batteries are composed of a chemical substance which can generate voltage which can be used in a circuit. There are two kinds of batteries: dry cell and wet cell batteries. Below is an example of a dry cell. The zinc container of the dry cell contains a moist chemical paste surrounding a carbon rod suspended in the middle.

18. Wet cell batteries are most commonly associated with automobile batteries. A wet cell contains two connected plates made of different metals or metal compounds in a conducting solution. Most car batteries have a series of six cells, each containing lead and lead oxide in a sulfuric acid solution.

19. How is Electrical Power calculated? Electrical Power is the product of the current (I) and the voltage (v) The unit for electrical power is the same as that for mechanical power in the previous module – the watt (W) Example Problem: How much power is used in a circuit which is 110 volts and has a current of 1.36 amps? P = I V Power = (1.36 amps) (110 V) = 150 W

20. How is electrical energy determined? Electrical energy is a measure of the amount of power used and the time of use. Electrical energy is the product of the power and the time. Example problem: E = P X time P = I V P = (2A) (120 V) = 240 W E = (240 W) (4 h) = 960Wh = 0.96 kWh