Question

An electron is held 1 cm from a negative point charge and then moved until it is 15cm from the point charge. What happens to the potential energy of the system? The potential energy of the system will increase. The potential energy of the system will decrease. The potential energy of the system will remain constant.

Answer 1

1 32 1 = 2 & 0.01 Let electron has charge dy=-e • and another negative point charge has charge + 2 = -q When electron is at distance 1 cun from negative point charge , potentiel energy of system is, Ui 9,92 Kl-e)(-9) og 4000 U = keq I = keq x 102 J = 100 keq I 0-01 Ui= 100 keq J electron is moued to 15cmg clleétuie potential energy of_systeme will be U z kl-e)1-9) I loo keq I 158 10-2 U4 = 6.67 keq 3 5 When 6

o 1 Therefore as electron is moved from 1 cu to 15 cm, Potential energy of the system decreases This can also be seen from the formala of potential energy o which is U= kaq 2 r 5 oo U x 1 r 5 so as & increases, U must decrease option (6)