1 / 29

FUSES

FUSES. explaining how fuses work. fuses and earthing. choosing the correct fuse. alternating current(H). resources. EXPLAINING HOW A FUSE WORKS. next. previous. How does a fuse work?. We should draw a fuse like this. to show that the fuse is a thin

laurayoung
Download Presentation

FUSES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. FUSES explaining how fuses work fuses and earthing choosing the correct fuse alternating current(H) resources

  2. EXPLAINING HOW A FUSE WORKS next previous

  3. How does a fuse work? We should draw a fuse like this to show that the fuse is a thin strand of wire which melts easily if too much current flows ( a fault). next previous

  4. battery switch Short circuit fuse lamp next previous

  5. battery switch Short circuit (fault) fuse lamp next previous

  6. HOW FUSES WORK Too much current flowing causes the fuse wire to This makes a gap and breaks the _________ so that no _________ flows. The job of a fuse is to protect the device it is connected to and to prevent electrical _______ from developing. • fault occurs • large current flows • heats and melts the fuse • breaks the circuit • stops the current flowing next previous

  7. Answers Melt Circuit Current Fire

  8. FUSES AND EARTHING next previous

  9. Step by step analysis for no earth • The fault develops (live wire touches the metal case) 2. The metal case becomes LIVE 3. A teacher wants to make a cup of coffee 4. OUCH! next previous

  10. Step by step analysis (with the case earthed) • The fault develops (live wire touches the metal case) next previous

  11. Step by step analysis (with the case earthed) • The fault develops (live wire touches the metal case) 2. Earth wire provides a low resistance path for current so a large current flows 3. The fuse melts and breaks the circuit 4. Electric current stops flowing and the live wire is now safe next previous

  12. Step by step analysis (with the case earthed) • The fault develops (live wire touches the metal case) 2. Earth wire provides a low resistance path for current so a large current flows 3. The fuse melts and breaks the circuit 4. Electric current stops flowing and the live wire is now safe next previous

  13. Metal wire touches the metal case Case becomes LIVE (230volts, a.c.) This could cause a fatal shock Kettles with a plastic case don’t need to be earthed next previous

  14. Good earthing provides an easy path for the current We call this easy path a low resistance path The low resistance draws a big current next previous

  15. The large current flows through the fuse Large current will cause heating It is vital that the fuse is the weakest link in the circuit next previous

  16. The fuse melts and makes a gap in the circuit The current stops flowing The metal case is not live any more The fuse has protected the kettle and us next previous

  17. CHOOSING THE CORRECT FUSE next previous

  18. Choosing the correct fuse Find out the current rating for the device Choose the fuse which is just above this current If the fuse is the same as the current rating you must choose the next fuse up next previous

  19. Choosing the correct fuse Fuses available 2, 3, 5, 8, 10 and 13Amp

  20. Choosing the correct fuse Fuses available 2, 3, 5, 8, 10 and 13Amp next previous

  21. Choosing the correct fuse Fuses available 2, 3, 5, 8, 10 and 13Amp next previous

  22. alternating current (a.c.) Higher level next previous

  23. The current changes direction (a.c.) The live wire goes above and below the axis The neutral remains at 0Volts all the time p.d. (volt) next previous

  24. The live pd (voltage) goes above and below the axis The pd (voltage) changes between + and – values This only happens for the live wire p.d. (volt) + + + _ _ next previous

  25. The mains voltage is 230Voltsac Only the live wire alternates (changes) The neutral wire stays at 0volts +230Volts +230Volts +230Volts -230Volts -230Volts 0Volts p.d. (volt) + + + _ _ next previous

  26. Mains electricity is alternating current a.c. Mains potential difference is 230volts 50 cycles per second (frequency is 50Hertz) Normal current is about 10 Amps If too much current flows the fuse melts next previous

  27. A D E B F C Draw these oscilloscope traces into you books Match the trace letter traces to the correct number 1 earth voltage 3 Small ac supply 5 1.5V battery 2 3Volt battery 4 large ac supply 6 flat battery

  28. 2 3Volt battery 1 earth voltage A D 6 flat battery 5 1.5V battery E B 4 large ac supply 3 Small ac supply F C ANSWERS!

  29. END next previous

More Related