Why should the area of cross-section of the meter-bridge wire be uniform ? Explian
Answers
Answer:
Explanation:
IT consists of a wire of length 1 m and of uniform cross-sectional area stretched taut and clamped between two thick metallic strips bent at right angles with two gaps across which resistors are to be connected. The end points where the wire is clamped are connected to a cell through a key. One end of a galvanometer is connected to the metallic strip midway between the two gaps. The other end of the galvanometer is connected to a jockey which moves along the wire to make electrical connection. R is an unknown resistance connected across one of the gaps. Across the other gap, we connect a standard known resistance S. The jockey is connected to some point D on the wire, a distance l
1
cm from the end A.The portion AD of the wire has a resistance R
cm
l
1
, where R
cm
is the resistance of the wire per unit centimeter. The portion DC of the wire similarly has a resistance R
cm
(100−l
1
).
The meter bridge works on the principle of Wheatstone bridge. At balance condition:
S
R
=
R
cm
(100−l
1
)
R
cm
l
1
=
100−l
1
l
1