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Electricity
- 1. Electricity Part I –Circuits
- 2. People Benjamin Franklin Thomas Edison Have you heard of these people? Why are they important?
- 3. Benjamin Franklin Provedthat lightning was electricity by flying a kite in a lightning storm Helped people understand the principles of electricity • Thomas Edison – Invented the electrical light bulb
- 4. What is electricity? Electricity is a form of energy It is caused by a flow of tiny particles called electrons through a material
- 5. Electricity Electricity is aflow of electric charges along a wire.
- 6. Electricity Electricity is aflow of electric charges along a wire.
- 7. Electricity Electricity is aflow of electric charges along a wire.
- 8. Electricity Electricity is aflow of electric charges along a wire.
- 9. Electricity Electricity is aflow of electric charges along a wire.
- 10. Electricity Electricity is aflow of electric charges along a wire.
- 11. Electricity Electricity is aflow of electric charges along a wire. This flow of electric charge is called a current. Current is measured in the units of Amps (A).
- 12. What is anElectrical Circuit? A circuit is an electrical device that provides a path for electricity to flow
- 13. Complete or Incomplete? A complete circuit is where all the components of a circuit are joined up and there are no gaps The pathway for electricity is complete
- 14. Complete or Incomplete? An incomplete circuit is where the pathway for electricity is broken The electricity cannot flow
- 15.
- 16. Component Symbols –a cell The cell stores chemical energy and transfers it to electrical energy when a circuit is connected. The long line is the positive end The short line is the negative end
- 17. Battery When twoor more cells are connected together we call this a Battery. The cells chemical energy is used up pushing a current round a circuit. It is important that each cell faces the right way
- 18. Switch A switchcan be open (as shown) or closed When the switch is open, the circuit is incomplete – no electricity can flow What happens when the switch is closed?
- 19. Bulb / Lamp The lamp lights up when electricity flows through it What would happen to a lamp if there was an open switch in the circuit?
- 20. Wires The wires whichcarry electricity consist of two parts: • The metal wires (conductor). • The plastic coating around the metal wires (insulator). • Prevents people from being electrocuted. wires
- 21. Voltmeter The voltmetermeasures the voltage of the circuit We will discuss this in another lesson
- 22. Ammeter The ammetermeasures the current in the circuit We will discuss this in another lesson
- 23. Resistor A resistorcan change the amount of current in a circuit In a variable resistor, the resistance can be changed.
- 25.
- 26. Variable resistors Look atFigure 17.6 on page 207. Path of current flow Terminal A metal bar sliding contact coils of wire Terminal B
- 27. Variable resistors Look atFigure 17.6 on page 207. The sliding contact can be adjusted so that the current passes through only a few coils of wire or many coils of wire. If the sliding contact is near Terminal A : current passes through many coils of wire = high resistance If the sliding contact is near Terminal B: current passes through a few coils of wire = low resistance
- 28. Variable resistors Turn thedial here for low resistance higher resistance
- 29. Fuse A fuseis a safety device When the current is too high, the fuse breaks Example The wire inside a 3A fuse will melt when the current is greater than 3A.
- 30. Motor A motorcan be fitted into a circuit What do you think happens to a motor in a complete circuit?
- 31.
- 33. types of circuit Thereare two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
- 34. The components areconnected 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.
- 35. PARALLEL CIRCUITS The currenthas a choice of routes (paths). The components are connected side by side. If one bulb ‘blows’ there would still be a complete circuit to the other bulb so it stays lit.
- 36. measuring current Electric currentis measured in amps (A) using an ammeter connected in series in the circuit. A
- 37. measuring current A A Thisis how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT
- 38. measuring current SERIES CIRCUIT PARALLELCIRCUIT • current is the same at all points in the circuit. 6A 6A 6A • current is shared between the components 4A 4A 3A 1A
- 39. copy the followingcircuits and fill in the missing ammeter readings. ? ? 4A 4A 4A 3A ? ? 1A ? 3A 1A 1A
- 40. measuring voltage The ‘electricalpush’ which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeter V
- 41. Different cells producedifferent voltages. The bigger the voltage supplied by the cell, the bigger the current (the cell gives a bigger push to the electrons). measuring voltage
- 42. measuring voltage Unlike anammeter a voltmeter is connected across the components (in parallel) Scientist usually use the term Potential Difference (pd) when they talk about voltage.
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- 44.
- 46. measuring voltage V This ishow we draw a voltmeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT V
- 47.
- 48. series circuit 1.5V • voltageis shared between the components 1.5V 3V
- 49. • voltage isthe same in all parts of the circuit. 3V parallel circuit 3V 3V
- 50. measuring current &voltage V V 6V 4A A A a)
- 51. measuring current &voltage V V 6V 4A A A A b)
- 52. answers 3V 3V 6V 4A 4A 6V 6V 6V 4A4A 2A 2A 4A a) b)