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# Electricity

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### Transcript

• 1.
• 2. Atoms…
• Have neutrons , protons , and electrons .
• Protons are positively charged
• Electrons are negatively charged
• 3. Electrons…
• Are located on the outer edges of atoms…they can be moved .
• A concentration of electrons in an atom creates a net negative charge.
• If electrons are stripped away, the atom becomes positively charged.
• 4. The world is filled with electrical charges : + - + + + + + + + + + - - - - - - - - -
• 5. What is this electrical potential called?
• Static Electricity
- - - - - - - + + + + +
• 6. Static Electricity
• The build up of an electric charge on the surface of an object.
• The charge builds up but does not flow.
• Static electricity is potential energy . It does not move. It is stored .
• 7. Static Discharge…
• Occurs when there is a loss of static electricity due to three possible things:
• Friction - rubbing
• Conduction – direct contact
• Induction – through an electrical field (not direct contact)
• 8. Electricity that moves …
• Current : The flow of electrons from one place to another.
• Measured in amperes (amps)
• Kinetic energy
• 9. How can we control currents?
• With circuits .
• Circuit : is a path for the flow of electrons. We use wires .
• 10. There are 2 types of currents:
• Direct Current (DC) – Where electrons flow in the same direction in a wire.
• 11. There are 2 types of currents:
• Alternating Current (AC) – electrons flow in different directions in a wire
• 12. simple circuits Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires
• 13. simple circuits When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.
• 14. circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;
• 15. circuit diagrams In circuit diagrams components are represented by the following symbols; battery switch motor ammeter voltmeter resistor
• 16. types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
• 17. The components are connected end-to-end, one after the other. They make a simple loop for the current to flow round. SERIES CIRCUITS If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
• 18. PARALLEL CIRCUITS The current has a choice of routes. The components are connected side by side. If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.
• 19. measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
• 20. measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A
• 21. measuring current SERIES CIRCUIT PARALLEL CIRCUIT
• current is the same
• at all points in the
• circuit.
2A 2A 2A
• current is shared
• between the
• components
2A 2A 1A 1A
• 22. Conductors vs. Insulators
• Conductors – material through which electric current flows easily .
• Insulators – materials through which electric current cannot move .
• 23. Examples
• Conductors :
• Metal
• Water
• Insulators :
• Styrofoam
• Rubber
• Plastic
• Paper
• 24. What is Resistance?
• The opposition to the flow of an electric current, producing heat .
• The greater the resistance, the less current gets through.
• Good conductors have low resistance.
• Measured in ohms.
• 25. What Influences Resistance?
• Material of wire – aluminum and copper have low resistance
• Thickness – the thicker the wire the lower the resistance
• Length – shorter wire has lower resistance
• Temperature – lower temperature has lower resistance
• 26. What is Voltage?
• 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.
• 27. Difference between Volts and Amps
• Example – you could say that…
• Amps measure how much water comes out of a hose.
• Volts measure how hard the water comes out of a hose.
• 28. Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance.
• Resistance = Voltage / Current
• Ohms = Volts / Amps
• 29. Practice with Ohm’s Law 8 48 6 5 45 9 15 30 2 10 150 15 25 100 4 Amps Volts Ohms