CHAPTER ONE
1.1 CHAPTER ONE
CHAPTER ONE
1.1 INTRODUCTION
In many electrical measurements, standard variable
resistances are required. These standard resistances come in various forms and
shapes. The resistance box is one of them.
These resistance boxes are imported and in most cases very
expensive. Most schools can therefore not afford to buy enough for the use of
there students. It is therefore important for technologists to be able to
improvise using locally available materials.
Also, during the course of designing and construction,
student technologists are really exposed to more practical works in order to
acquired a lot of experience on how to make use and handle many laboratory
tools, equipments and apparatus.
We have two different, types of resistance boxes which
includes:
(a) Decade type
(b) Plug type
In decade type, the coil of each resistance are connected
in series, and there is a rotary switch which also aids in contact with each
other. The switching used are of high quality compared with the resistance of
the coils which they are selected.
In plug type, no switches are required instead, their
resistance is varied by means of plugs. The resistance coils are formed across
gaps with a thick brass bar, and the gaps are formed in the holes being drilled
to receive the short circuiting plugs.
1.2 AIM OF THE PROJECT
This project aim at presenting precisely the process of
construction of a resistance box, which is an imported equipment in the physics
laboratory.
Most practical work involve the use of resistors of fixed
value that are fixed into and later removed from the circuit. The replacement
of a particular resistor of a given value may lead to destruction of the
resistor so an alternative way for guiding against this is by use of variable
resistance box.
This resistance box is to provide a resistance range
between two and eleven (2-11W
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