Answer to Question #306389 in Electric Circuits for mela

Question

1.The potential energy of a certain system of two charges increases as the charges are moved farther apart.What does this tell us about the sign of the charges?why?

2.Show that volt per meter is the same as newton per coulomb.

3.A student said"electric potential is always proportional to potential energy,why bother with the concept of potential at all?How would you respond?

Answer 1

Answer

a)

• The charges are positive.
• Their potential vs interatomic distance graph falls in the negative region of the potential axis.
• As they move farther apart the potential l energy changes from highly negative to zero at infinity.

b)

$\qquad\qquad \begin{aligned} \small Vm^{-1}&=\small (JC^{-1})m^{-1}\\ &=\small (Jm^{-1})C^{-1}\\ &=\small kgm^2s^{-2}.m^{-1}.C^{-1}\\ &=\small kgms^{-2}.C^{-1}\\ &=\small NC^{-1} \end{aligned}$

c)

• Potential energy is a quantity dependent on the charge, potential is independant.
• There could be different potential energies for the same potential with different charges.

$\qquad\qquad \begin{aligned} \small q_1>&q_2>q_3\\ \small E_1=Vq_1,\,\,E_2&=\small Vq_2,\,\,E_3=Vq_3\\ \therefore,\\ \small E_1>&\small E_2>E_3\\ \small \text{on the other hand}\\ \small V_1>&\small V_2>V_3\cdots(wrong\,as\,V_1=V_2=V_3=V) \end{aligned}$