Current Electricity. ScienceLinks 9, Unit 4 SciencePower 9, Unit 3

Transcription

1 Current Electricity ScienceLinks 9, Unit 4 SciencePower 9, Unit 3

2 Current Electricity The flow of negative charges (electrons) through conductors Watch the BrainPOPs: Electricity Current Electricity

3 Activity: Create a simple circuit Materials: 1 battery, 1 flashlight bulb, 2 wires Procedure: 1. Connect the battery and bulb in a way that will make the bulb light up. 2. Sketch the arrangement in your notes.

4 Activity continued Analysis: 1. Explain why there must be a certain arrangement of materials for the bulb to light up. 2. Where does the energy come from to make the bulb light up? 3. What is happening inside the conductors in your circuit to make the bulb light up? (i.e. what is going on with the atoms and their charges?)

5 Source A device that supplies electrical energy to operate electrical equipment A constant source of electrical energy can drive a steady current or flow of charges

6 Load A device that uses electrical energy to run Loads slow down, or resist, moving charges

7 Loads Energy converters Change electrical energy into a useful form of energy Light Heat Motion

8 Potential Difference The change in energy of a charge after it passes through a source or a load Charges gain energy when they pass through a source Charges lose energy when they pass through a load

9 Activity: Creating Potential Difference 1. Everyone stand up on one side of the room. 2. Chemical reaction and charge separation: some people (electrons) walk to the other side of the room, the rest stay This is the Potential difference or voltage 3. Now demonstrate the following: Increase the voltage of this source Show what would happen to the charges when we connect this source to a load Show what might happen when a battery runs out of power

10 Batteries Use chemical changes to separate charges Separating the charges creates potential electrical energy or a potential difference The potential difference is also called the voltage; measured in Volts (V) E.g.: 1.5V, 3V, 120V

11 Batteries Higher voltage or potential energy = more charge separation

12 Current The moving charges from the source to the load and back Charges cannot build up in a conductor therefore current is the same throughout a conductor Current (I) is measured in Amperes (A)

13 Activity: Creating Current 1. Everyone stand up and form a circle around the perimeter of the desks 2. Start walking slowly What strength current would this be? 3. How can we demonstrate a stronger current?

14 Meters Voltmeter measures the voltage (potential difference) across/through a source or load Ammeter measures the current in a circuit

15 Concept Check 1. What is required to connect a source of electricity to a load? 2. Use the terms source, current, and load to describe how the heating element in an oven probably works. 3. Use words, diagrams or a graphic organizer to explain what happens to electric charges as they pass through a load.

16 Video Watch the Bill Nye video, Electricity on You Tube

17 Electrical Circuits A connection between a source, load, and conductor (i.e. wires) that creates a complete path through which current can flow. All charges must return to the source, so a circuit must be a closed loop

18 A Switch Controls the flow of current by opening (breaking) or closing the circuit

19 Circuit Diagrams Symbols used to represent parts of a circuit Source Conducting Wire Load (resistance) Switch Open Switch Closed

20 Practice: Label the Parts

21 Notice the Meters How are they connected differently? Why do you think this is so?

22 Meters Since the current is the same throughout a circuit an ammeter can be connected at any location within the circuit Voltmeters measure the potential difference of charge between two points so they must be connected on either side of or across a source or load in the circuit

23 Labs 1. Complete the Creating Simple Circuits lab as directed on the lab sheet. 2. Complete the Circuit Builder Gizmo

24 Resistance (R) Describes the amount that current is slowed down by a load Measured in ohms (Ω) As charges pass through a load they lose energy because it has been converted into light, heat, etc.

25 Ohm s Law: V = IR Potential difference and resistance affect the current What do you think would happen to the current if you kept the potential difference of the source the same and increased the resistance by adding more loads to a circuit? The charges leaving the source have the same amount of energy so as the resistance increases the current would decrease. If the loads were light bulbs they would become dimmer as more were added.

26 Ohm s Law animation View and discuss the animation on phet:

27 Use the graphs to explain how changing the potential difference of the source and changing the resistance of the load affect the current flowing through this closed circuit.