3 cov lus nug txog qhov sib txawv ntawm qhov muaj peev xwm
1. Ib lub zog hluav taws xob raug txav mus rau hauv ib lub teb hluav taws xob sib xws nrog lub zog ntawm 2√3 N ntawm qhov deb ntawm 20 cm. Yog tias qhov kev taw qhia ntawm lub zog yog nyob rau ntawm lub kaum sab xis ntawm 30 o rau qhov kev hloov chaw ntawm lub zog hluav taws xob, qhov sib txawv ntawm lub zog hluav taws xob ntawm qhov pib thiab qhov kawg ntawm lub zog hluav taws xob yog dab tsi.
Paub:
Lub zog (F) = 2√3 N
Qhov Nrug Deb (s) = 20 cm = 0.2 m
Lub kaum sab xis (θ) = 30 o
Xav tau: Qhov sib txawv ntawm lub zog hluav taws xob
tshuaj:
Txoj haujlwm ntawm kev hloov tus nqi +q ntawm a mus rau b yog sib npaug rau qhov sib txawv ntawm lub zog hluav taws xob ntawm cov ntsiab lus a thiab b.
ΔEP = ΔW
Yog tias qhov kev taw qhia ntawm lub zog F nrog rau qhov kev taw qhia ntawm kev hloov pauv nqi +q yog lub kaum sab xis θ, ces txoj haujlwm ntawm kev hloov pauv nqi +q los ntawm a mus rau b yog:
ΔW = F Δs cos θ = ( 2 √ 3 )(0,2)(cos 30) = (0,4 √ 3 )(0,5 √ 3 ) = (0,2)(3) = 0,6 Joule
2. Yog tias lub zog thiab lub peev xwm ntawm cov capacitors paub tias yog 5 µC thiab 20 µF, raws li, txiav txim siab qhov sib txawv ntawm cov capacitors.
Paub:
Lub zog hluav taws xob (q) = 5 µC = 5 x 10 -6 C
Lub peev xwm ntawm lub capacitor (C) = 20 µF = 20 x 10 -6 F
Xav tau: Capacitor qhov sib txawv (V)
tshuaj:
Cov mis rau qhov sib txawv ntawm lub peev xwm ntawm lub capacitor, lub peev xwm ntawm lub capacitor thiab tus nqi:
V = q / C = (5 x 10 -6 ) / 20 x 10 -6 = 5/20 = 0,25 Volts
3. Ob lub ntsiab lus them QA = -4 µC thiab QB = 8 µC sib nrug 16 cm. Txheeb xyuas lub zog hluav taws xob ntawm qhov chaw nruab nrab ntawm ob lub nqi.
Paub:
Tus nqi hluav taws xob 1 (QA ) = 4 x 10 -6 C
Lub zog hluav taws xob 2 (QB ) = 8 x 10 -6 C
Qhov Nrug Deb (r) = 8 cm = 0,08 m
Coulomb tas li (k) = 9 × 10 9 Nm 2 /C 2
Xav tau: Lub zog hluav taws xob ntawm C (V C )
tshuaj:
V A = k Q / r = (9 × 10 9 )(4 x 10 -6 ) / 0,08 = (36 × 10 3 ) / 0,08 = -450 Volts
V B = k Q / r = (9 × 10 9 )(8 x 10 -6 ) / 0,08 = (72 × 10 3 ) / 0,08 = 900 Volts
Lub zog hluav taws xob ntawm C (V C ) = 900 - 450 = 450 Volts
