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Electricity and Magnetism

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Displacement from a Line of Charge: Field Point Above the Edge

EANDM-FTPNRY

Figure 1 depicts a line of charge of length $l$, upon which a linear charge density of $\lambda = 7.33 \: \rm \frac{nC}{m}$ has been placed.

Figure 1. Timothy Black. Created for Albert.io. Copyright 2016. All rights reserved.

A field point $P$ exists a distance $z$ above the left edge of the line of charge. Figure 2 shows the electric potential $V$ at the field point as a function of the line length $l$.

Figure 2. “Timothy Black. Created for Albert.io. Copyright 2016. All rights reserved.”

What is the displacement $z$ of the field point from the end of the line?

A

$z = 21.7 \text{ cm}$

B

$z = 8.18 \text{ cm}$

C

$z = 4.61 \text{ cm}$

D

$z = 10.0 \text{ cm}$