Two point charges q 1=+2.25nC and q 2=6.60nC are 0.100 m apart. Point A is midwa
ID: 1526677 • Letter: T
Question
Two point charges q1=+2.25nC and q2=6.60nC are 0.100 m apart. Point A is midway between them; point B is 0.080 m from q1and 0.060 m from q2. (See (Figure 1) .) Take the electric potential to be zero at infinity.
Part A
Find the potential at point A.
Express your answer in volts to three significant figures.
Part B
Find the potential at point B.
Express your answer in volts to three significant figures.
Part C
Find the work done by the electric field on a charge of 2.75 nC that travels from point B to point A.
Express your answer in joules to two significant figures.
91 0.050 m- 0.050 m 92Explanation / Answer
The potential at a point is given by
V = Ke * q/r
where
Coulomb constant ke = 9*10^9 N*m^2/C^2
Electric charge = q
electric long distance = r
(a) the potential at point A
Potential generated at point A by q1
V1 = Ke*q1/r1
Electric charge
q1 = +2.25*10^-9 C
distance
r1 = 0.050 m
evaluate numerically
V1 = 9*10^9 * 2.25*10^-9/0.050
= +405 volt
Potential generated at point A by q2
V2 = ke*q1/r1
where
Electric charge
q2 = -6.60*10^-9 C
distance
r2 = 0.050 m
evaluate numerically
V2 = 9*10^9 * -6.60*10^-9/0.050
V2 = -1188 volt
The potential at point A is equal to
VA = V1 + V2
= 405 - 1188
= -783 volt
(b) the potential at point B
Potential generated at point B by q1
V1 = ke * q1/r1
where
Electric charge
q1 = +2.25*10^-9 C
distance
r1 = 0.080 m
evaluate numerically
V1 = 9*10^9 * +2.25*10^-9/0.080
= +253 volt
Potential generated at point B by q2
V2 = ke * q2/r2
where
Electric charge
q2 = -6.60*10^-9 C
distance
r2 = 0.060 m
evaluate numerically
V2 = 9*10^9 * -6.60*10^-9/0.060
= -990 Volt
The potential at point B is equal to
VB = V1 +V2
= +253 V - 990 V
= -737 Volt
(c) the work done by the electric field on a charge of 2.75 nC that travels from point B to point A
The work done by the electric field is given by
WAtoB = -q*(vB-vA)
where
VB = -737 V , VA = -783 V and q = 2.75*10^-9 C
evaluate numerically
wAtoB = -2.75*10^-9 * (-737 +(- 783 ))
= -1.265*10^-7 J
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