2-5 Electricity and safety (2.4)

Electricity and safety 
(p. 78)
Stationary
- Wrinting book and iPad
- Pen, pencil and geotriangle
- Calculator


Schoolbags in
the cupboard
Phones in phone bag
Bluetooth 
- ON
- VPN off
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Slide 1: Slide
NatuurkundeMiddelbare schoolhavoLeerjaar 3

This lesson contains 11 slides, with interactive quiz and text slides.

time-iconLesson duration is: 45 min

Items in this lesson

Electricity and safety 
(p. 78)
Stationary
- Wrinting book and iPad
- Pen, pencil and geotriangle
- Calculator


Schoolbags in
the cupboard
Phones in phone bag
Bluetooth 
- ON
- VPN off

Slide 1 - Slide

Lesson goals:
Leg uit wat de volgende woorde betekenen:
  • I can distinguish between contact resistance and bodily resistance
  • I can distinguish between single and double insulation
  • I know what a fuse is
  • I know what an earth is and how a earth leakage works

Slide 2 - Slide

DANGERS:
  • When there is a high current 
       passing through a conductor
       they get so hot that it can
       cause a fire.
  • When touching a conducting 
       material you experience an
       electric shock.

Slide 3 - Slide

Current through your body
- WHen the current passing  
   through your body is small, you 
   maintain controll over your 
   muscles. 
- If the current through your body 
   is too big then you loose control 
   and your muscles can not relax.

Slide 4 - Slide

Electrical resistance of your body and contact resitance

The magnitude of the current depends on two things:
1 - How great the voltage is
2 - How great the resistance of the body  is

The total resistance is the sum of these two

I=RV
Dry skin = great contact resistance      wet skin =low contact resistance

Slide 5 - Slide

Single and double insulation
  • The conducting wires in a  household elecrrical system have been selected to allow 16 A current to pass through it. 
  • The conducting wire has been insulated with pvc.
  • This prevents you from getting a shock or a short circuit to occur.
  • Some apparatus have double insulation

Slide 6 - Slide

Safety preacuations in the metercabinet      
     FUSE
- Each circuit has its own circuitbreaker or circuit fuse
- If the currentis greater than  
   16 A the circuitbreaker will flip
   switching off the current.
- This prevents a fire from starting.

Slide 7 - Slide

Earth leakage
- The earth leakage compares the current in the phase wire and the neural wire.
- If they are the same size there is no problem and the earth leakage will allow the current to pass through.
- If the difference in curertn between the
the phase and the neutral wire is more tan 30 mA, 
teh earth leakage flips.

Slide 8 - Slide

Earth
- This prevents the leakage current from passing through someones body.
- Therefore a green yellow earth runs from the outer casting of an apparatus back to the socket
and then to the earth rail in the
meter cabinet.

Slide 9 - Slide

What did you learn?

Slide 10 - Mind map

             Do the following
42, 43 and 44 and the test yourself of paragraph 2.4
If you are done: 
timer
15:00
REGELS:
  • Digital method


  • Help? Use your book
  • No discussion

  • In 15 minutes time we discuss the questions
For extra exercise also make question 40 and 41 in the digital method

Slide 11 - Slide