1. Xam qhov loj thiab kev coj ntawm lub zog hluav taws xob ntawm qhov chaw A nyob ntawm 5 cm ntawm qhov chaw them Q = +10 μC. k = 9 x 10 9 Nm 2 C −2 , 1 μC = 10 −6 C)
Paub:
Lub zog hluav taws xob (Q) = +10 μC = +10 x 10 -6 C
Qhov nrug ntawm qhov chaw A thiab qhov chaw them nqi Q (r A ) = 5 cm = 0.05 m = 5 x 10 -2 m
k = 9 x 10 9 Nm 2 C −2
Xav tau: Qhov loj thiab kev coj ntawm lub zog hluav taws xob ntawm qhov chaw A
Tshuaj:
Kev taw qhia ntawm lub zog hluav taws xob ntawm qhov chaw A:
Lub zog hluav taws xob yog qhov zoo yog li ntawd qhov kev taw qhia ntawm lub teb hluav taws xob yog deb ntawm lub zog hluav taws xob thiab cov ntsiab lus A.
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2. Xam qhov loj thiab kev coj ntawm lub teb hluav taws xob ntawm qhov chaw P nyob ntawm 10 cm ntawm qhov chaw them Q = -2 0 μC. k = 9 x 10 9 Nm 2 C −2 , 1 μC = 10 −6 C.
Paub:
Lub zog hluav taws xob (q) = -20 μC = -20 x 10 -6 C
Qhov nrug ntawm qhov chaw P thiab lub zog hluav taws xob (rP ) = 10 cm = 0.1 m = 1 x 10 -1 m
k = 9 x 10 9 Nm 2 C −2
Xav tau: Qhov loj thiab kev coj ntawm lub zog hluav taws xob ntawm qhov chaw P
Tshuaj:
Kev taw qhia ntawm lub zog hluav taws xob ntawm qhov chaw A:
Lub zog hluav taws xob yog negative yog li ntawd lub zog hluav taws xob ntawm lub teb hluav taws xob mus rau lub zog hluav taws xob.
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3. Ob lub ntsiab lus hluav taws xob raug sib cais los ntawm qhov deb ntawm 40 cm. Qhov loj thiab qhov kev taw qhia ntawm lub zog hluav taws xob ntawm qhov chaw P ntawm ob lub ntsiab lus hluav taws xob, uas yog 20 cm ntawm qhov chaw A yog dab tsi?
Paub:
Them A (q A ) = -2 μC = -2 x 10 -6 C
Them B (qB ) = + 4 μC = +4 x 10 -6 C
Qhov nrug ntawm lub zog them A thiab qhov chaw P (r AP ) = 20 cm = 0.2 m = 2 x 10 -1 m
Qhov nrug ntawm lub zog them B thiab qhov chaw P (r BP ) = 20 cm = 0.2 m = 2 x 10 -1 m
Xav tau: Qhov loj thiab kev coj ntawm lub zog hluav taws xob ntawm qhov chaw P.
Tshuaj:
Tus nqi A yog qhov tsis zoo yog li ntawd qhov kev taw qhia ntawm lub zog hluav taws xob taw tes rau Q A (mus rau sab laug).
Tus nqi B yog qhov zoo yog li qhov kev taw qhia ntawm cov ntsiab lus hluav taws xob nyob deb ntawm Q B (mus rau sab laug).
Tag nrho cov hluav taws xob teb ntawm qhov chaw A:
E = E A + E B
E = (4.5 x 105 ) + (9 x 105 )
E = 13.5 x 10 5 N/C
Qhov kev taw qhia ntawm lub zog hluav taws xob taw tes rau Q A (mus rau sab laug).
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4. Qhov loj ntawm lub teb hluav taws xob yog xoom ntawm…
Tus nqi A yog qhov zoo thiab tus nqi B yog qhov zoo yog li qhov loj ntawm lub teb hluav taws xob yog xoom nyob ntawm qhov chaw P, ntawm ob qho tib si.
Paub:
Them A (q A ) = + 20 μC = +20 x 10 −6 C
Tus nqi B (qB ) = +40 μC = +40 x 10 −6 C
k = 9 x 10 9 Nm 2 C −2
Qhov nrug ntawm lub zog A thiab lub zog B = 20 cm
Tus nqi hluav taws xob ntawm tus nqi hluav taws xob A thiab qhov chaw P (r AP ) = a
Qhov nrug ntawm tus nqi B thiab qhov chaw P (r BP ) = 20 - a
Xav tau: Qhov loj ntawm lub zog hluav taws xob yog xoom nyob ntawm….
Tshuaj:
Qhov loj ntawm lub zog hluav taws xob uas tsim los ntawm tus nqi A ntawm qhov chaw P
Tus nqi A yog qhov zoo yog li qhov kev taw qhia ntawm cov ntsiab lus hluav taws xob nyob deb ntawm tus nqi A (mus rau sab xis).
Qhov loj ntawm lub zog hluav taws xob uas tsim los ntawm tus nqi B ntawm qhov chaw P:
Tus nqi B yog qhov zoo yog li qhov kev taw qhia ntawm cov ntsiab lus hluav taws xob nyob deb ntawm tus nqi B (mus rau sab laug).
Tag nrho cov hluav taws xob teb ntawm qhov chaw P = 0:
Peb siv cov qauv quadratic los txiav txim siab a.
Qhov loj ntawm lub teb hluav taws xob yog xoom nyob ntawm 8 cm ntawm tus nqi A lossis 12 cm ntawm tus nqi B.
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5. Raws li daim duab hauv qab no, w ntawm no yog qhov taw tes P yog li ntawd lub teb hluav taws xob ntawm qhov taw tes P yog xoom? (k = 9 x 10 9 Nm 2 C −2 , 1 μC = 10 −6 C)
tshuaj
To xam lub zog hluav taws xob ntawm qhov chaw P, xav tias ntawm qhov chaw P muaj qhov them kuaj zoo. Q1 yog qhov zoo thiab Q2 yog qhov tsis zoo, yog li ntawd qhov P yuav tsum nyob rau sab xis ntawm Q2 los yog sab laug ntawm Q1Yog tias qhov chaw P nyob rau sab laug ntawm Q1lub zog hluav taws xob uas tsim los ntawm Q1 ntawm qhov chaw P nyob rau sab laug (deb ntawm Q1) thiab lub zog hluav taws xob uas tsim los ntawm Q2 ntawm qhov chaw P mus rau sab xis (mus rau Q1). Qhov kev taw qhia ntawm lub zog hluav taws xob yog qhov sib txawv kom ob lub zog hluav taws xob tshem tawm ib leeg kom lub zog hluav taws xob ntawm qhov chaw P yog xoom.
Paub:
Q 1 = +9 μC = +9 x 10 −6 C
Q 2 = -4 μC = -4 x 10 −6 C
k = 9 x 10 9 Nm 2 C −2
Qhov nrug ntawm tus nqi 1 thiab tus nqi 2 = 3 cm
Qhov nrug ntawm Q 1 thiab qhov chaw P (r 1P ) = a
Qhov nrug ntawm Q 2 thiab qhov chaw P (r 2P ) = 3 + a
Xav tau: qhov chaw ntawm qhov P kom lub zog hluav taws xob ntawm qhov P yog xoom
Tshuaj:
Point P nyob rau sab laug ntawm Q 1.
Lub teb hluav taws xob tsim los ntawm Q 1 ntawm qhov chaw P:
Tus nqi sim yog qhov zoo thiab Q 1 yog qhov zoo yog li qhov kev taw qhia ntawm lub teb hluav taws xob yog mus rau sab laug.
Lub teb hluav taws xob tsim los ntawm Q 2 ntawm qhov chaw P:
Tus nqi kuaj yog qhov zoo thiab Q 2 yog qhov tsis zoo yog li qhov kev taw qhia ntawm lub teb hluav taws xob yog mus rau sab xis.
Lub zog hluav taws xob ntawm qhov chaw A:
Siv cov qauv quadratic los txiav txim siab ib qho:
a = -1.25, b = -13.5, c = -20.25
Qhov nrug ntawm Q 2 thiab taw tes P (r 2P ) = 3 + a = 3 – 1.8 = 1.2 cm.
Point P nyob rau ntawm 1.2 cm sab xis ntawm Q 1.
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