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EARTH
NEUTRAL
MALUS’S
LAW
AND LIVE DEMO
LA10-980
INSTRUCTIONS FOR USE
EARTH NEUTRAL AND LIVE DEMO
LA10-980
INTRODUCTION
This apparatus provides a
convenient and safe method for
demonstrating the action of a fuse
and earth wire in protecting the
user in the event of a fault.
ENSURE THE PRECAUTIONS ON THE REVERSE OF THIS
LEAFLET HAVE BEEN READ AND UNDERSTOOD BEFORE
ATTEMPTING TO USE THIS APPARATUS
SETTING UP
Directions in brackets indicate reference to the diagram on the next
page.
 Ensure that the unit is switched off.
 Add a short length of the fuse wire provided between the wing
nuts on the plug (A)
 Ensure that the yellow and green earth wire is connected to the
kettle (Socket 1) and that the brown live wire is connected to the
filament (Socket 2)
 Connect a 12V D.C. supply to the input sockets (B) – ensuring
that correct polarity is observed. Switch both the supply and the
apparatus on.
 The LEDs in the kettle should light to indicate that the kettle is
functioning correctly.
 The unit is ready for use.
B
A
DEMONSTRATIONS
1) During all explanations the current path can be easily traced
from the PSU (Power station) through the socket, plug, wire and
appliance
2) Removing the earth wire from socket one can be shown to have
no effect on the operation of the kettle.
3) With the earth wire left disconnected, moving the live wire from
socket two to socket three (to indicate a fault has occurred
allowing the live wire to touch the metal case) will cause the
LEDs throughout the user to illuminate. Again the path from the
live wire through the user to ground can be easily traced.
4) With the unit switched off and the earth wire replaced in socket
one and the fault remaining (brown live wire in socket three) the
possible current paths may be traced. The path through the user
to ground still exists but the low resistance path through the
earth wire to ground will lead to a high current in the live wire
(and therefore the fuse) and on switching on, the fuse will
visibly glow and melt, breaking the circuit and rendering the
appliance safe.
PRECAUTIONS
The fuse wire will glow red hot before breaking and care must be
taken to avoid contact with the fuse during this time.
Ensure that the unit is switched off before replacing fuse wire.
The fuse wire is 40SWG tinned copper wire. Do not attempt to
use any wire of a different rating. Additional reels may be
purchaced from SciChem if required.
.
Lascells Ltd.,
Walkmill Business Park, Sutton Road, Market Drayton, Shropshire. TF9 2HT
Tel 01630 657 801
Fax 01630 656726
www.lascells.com