Two \"source\" charges +Q and -Q are fixed in place at the positions 93 shown. L

Question

Two "source" charges +Q and -Q are fixed in place at the positions 93 shown. Locations A-C are labeled on the diagram 1. Draw arrows on the diagram to represent the direction of the 2. A positive probe charge of +0.01 Coulombs is moved from A to lB electric field at locations A-C a. Is the work on the probe charge by the electric field positive, negative, or zero? Explain b. Is the change in electrical potential energy positive, negative, or zero Explain Is the electric potential difference AVAB-VB - VA positive, negative, or zero? Explain c.

Explanation / Answer

1. at A :

field due to -Q : upward

field due to +Q : upwrad

hence direction at A will be upward. (2E)

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at B :

field due to -Q : upward

field due to +Q : upwrad

hence direction at B will be upward. (E1 + E2)

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at A :

field due to -Q : upward at angle @ with -ve x aixs.

field due to +Q : upwrad at an angle @ with +ve x axis.
horizontal component are same same in magnitude (E cos@) but opposite in direction henc it will cancel out.

hence direction at C will be upward. (2 E sin@ )

2. charge is +ve hence +Q will repel but -Q will attract.

hence force on charge is upward.

and dispalcement is also upward.

hecnce work done by electric force will be +ve.

C) V = kq/ r

at A , Vnet = k (Q/r) + k (-Q /r) = 0

at B , Vnet = k(Q/r1) + k(-Q/r2) and r1 > r2

    Vnet < 0

so Vb - Va < 0

Ans, negative

b) PE = q deltaV = negative

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