A metal wire is 4.0 m and square cross-sectional area is 1.00 mm2. Resistivity of material of wire is 1.0/1000000 ohm metre. The wire is closely wound on a uniform wooden cylinder. If there are 100 coils which are in perfect contact witn one other,estimate the equivalent resistance of the arrangement. What is the arrangement like?
by solution:
Length of the coil=100*square root of 1/1000000 =0.1m
A=4*(1/1000000)/0.1=4/100000 m2
R=(1/1000000)*(0.1)/(4/1000000)=2.5/1000 ohm
But why?
current electricity
2007-10-19 11:02 pm
回答 (2)
2007-10-20 9:17 am
✔ 最佳答案
Since the coils are in contact with each other, the [conductor] formed by the wire now becomes a hollow cylindrical form.Length of the conductor (cylinder) = no. of turns x thickness of wire
= 100 x sqrt(10^-6) m = 0.1 m
where sqrt= square root
Cross sectional area of hollow cylindrical conductor = volume of wire/length of cylinder
= (4 x 10^-6)/0.1 m2 = 4 x 10^-5 m2
Thus using the formula for resistance R of a conductor
R = resistivity x length/cross-section area
R = (10^-6) x 0.1/4x10^-5 ohm = 2.5 x 10^-3 ohm
2007-10-20 7:18 am
Formula:
R = Pl / A, P -resisitvity, l -length, A -area..
By SI unit.
P = 1.0/1000000 ohm meter,
l = 4m
A=1mm2 = 0.000001m2
because, resistance is proportional to length,
inproportional to area..
OK?
R = Pl / A, P -resisitvity, l -length, A -area..
By SI unit.
P = 1.0/1000000 ohm meter,
l = 4m
A=1mm2 = 0.000001m2
because, resistance is proportional to length,
inproportional to area..
OK?
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