Chapter 3, Problem 3.9QP

(a)

Interpretation Introduction

Interpretation:

The ratio of electrostatic energy between the given charges and the ratio of distance in the given statements should be calculated by using the concept of electrostatic energy.

Concept Introduction:

Energy is the capacity to do work or transfer heat where work is the movement of a body using some force.  The SI unit of energy is joule ($\text{J}$).  Energy is in the form of kinetic energy or potential energy.  Kinetic energy is the energy associated with motion.  Potential energy is the energy possessed by virtue of position. Other forms of potential energy are chemical energy and electrostatic energy.

Electrostatic energy is the potential energy which results from the interaction of charged particles.  Oppositely charged particles attract each other and like particles charges repel each other.  The magnitude of the resulting electrostatic potential energy is directly proportional to the product of the two charges (${\text{Q}}_{\text{1}}{\text{ and Q}}_{\text{2}}$) divided by the distance between the two charges ($\text{d}$).

${\text{E}}_{\text{el}}\propto \frac{{\text{Q}}_{\text{1}}{\text{Q}}_{\text{2}}}{\text{d}}$

If the charges ${\text{Q}}_{\text{1}}{\text{ and Q}}_{\text{2}}$ are opposite (i.e., one positive and one negative), ${\text{E}}_{\text{el}}$ gets a negative value which means attraction.  Like charges (i.e., either both positive or both negative) result in a positive value of ${\text{E}}_{\text{el}}$ which indicates repulsion.

(b)

Interpretation Introduction

Interpretation:

The ratio of electrostatic energy between the given charges and the ratio of distance in the given statements should be calculated by using the concept of electrostatic energy.

Concept Introduction:

Energy is the capacity to do work or transfer heat where work is the movement of a body using some force.  The SI unit of energy is joule ($\text{J}$).  Energy is in the form of kinetic energy or potential energy.  Kinetic energy is the energy associated with motion.  Potential energy is the energy possessed by virtue of position. Other forms of potential energy are chemical energy and electrostatic energy.

Electrostatic energy is the potential energy which results from the interaction of charged particles.  Oppositely charged particles attract each other and like particles charges repel each other.  The magnitude of the resulting electrostatic potential energy is directly proportional to the product of the two charges (${\text{Q}}_{\text{1}}{\text{ and Q}}_{\text{2}}$) divided by the distance between the two charges ($\text{d}$).

${\text{E}}_{\text{el}}\propto \frac{{\text{Q}}_{\text{1}}{\text{Q}}_{\text{2}}}{\text{d}}$

If the charges ${\text{Q}}_{\text{1}}{\text{ and Q}}_{\text{2}}$ are opposite (i.e., one positive and one negative), ${\text{E}}_{\text{el}}$ gets a negative value which means attraction.  Like charges (i.e., either both positive or both negative) result in a positive value of ${\text{E}}_{\text{el}}$ which indicates repulsion.