Urgent. Plz help with how you do it.?

[匿名]

2017-02-06 1:02 pm

A straight, nonconducting plastic wire 8.50 cm long carries a charge density of 100 nC/m distributed uniformly along its length. It is lying on a horizontal tabletop.

a) Find the magnitude and direction of the electric field this wire produces at a point 6.00 cm directly above its midpoint.

b) If the wire is now bent into a circle lying flat on the table, find the magnitude and direction of the electric field it produces at a point 6.00 cm directly above its center.

回答 (1)

NCS

2017-02-07 2:59 am

✔ 最佳答案

a) The direction of the field above the wire is "up" since the wire is positively charged. The magnitude is given by
E = (kλ/z)[b/√(z² + b²) + a/√(z² + a²)]
where k = 8.99e9N·m²/C²
and λ = 100e-9 C/m
and z = 6.00 cm = 0.0600 m
and a = b = 8.50cm / 2 = 0.0425 m

b) the direction is still up, and for the same reason. The magnitude for a ring is given by
E = kλ2πRz / √(R² + z²)³
where k and λ are as above
and R = radius of ring = 0.0850m / 2π
and z = 0.0600 m

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參考: line: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elelin.html#c1 ring: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elelin.html#c2

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