# Electricity & Magnetism: Potential Field

• Cmertin
In summary, the problem involves calculating the work required to move a charge from one point to another in an electric field created by three point charges. The values of the potentials and positions of the charges are given. The equations used are W=q∆V, E≅-∆V/∆l, and F=q(-∆V/∆l). The answers for B, C, and D are incorrect, possibly due to incorrect measurements or calculations. The correct answers are 3.78×10^-9 J, -1.79×10^5 N/C, and Q3=4.8×10^-12C.
Cmertin

## Homework Statement

The lines show the equipotential contours in the plane of three point charges, Q1, Q2, and Q3. The values of the potentials are in kV as indicated for the +5, 0, and -5 kV contours. The positions of the charges are indicated by the dots.
[PLAIN]http://img824.imageshack.us/img824/4397/stupidpic.gif

A. Calculate the work required to move a charge of -0.63×10-12C from i to b.

B. Calculate the size of the electric field at g.

C. Calculate the size of the force on a charge of 4.80×10^-19 C at k.

D. Calculate the size of Q3. The magnitudes of the three charges are in the exact ratios of 1 to 2 to 3.

W=q∆V
E≅-∆V/∆l
F=q(-∆V/∆l)

## The Attempt at a Solution

B. I measured from the center of the Q3 charge to be 2.8 cm (.028m).
The change in voltage is 1KV/line so it is 5000V
E=-5000V/.028m=-1.79×10^5N/C --- It says that this is the wrong answer.

Last edited by a moderator:
C. I measured from the center of the Q3 charge to be 1.7cm (.017m) The change in voltage is 0.5KV/line so it is 2500VF=4.8×10^-19*(-2500V/.017m)= -3.53×10^-15N --- It says that this is the wrong answer. D. I assumed the magnitudes of the three charges are in the exact ratios of 1 to 2 to 3Q1=1×10^-12C Q2=2×10^-12C Q3=3×10^-12C ---- It says that this is the wrong answer. I would really appreciate if someone could point out where I went wrong.

## 1. What is an electric potential field?

An electric potential field is a region in space where a charged particle experiences a force due to the presence of other charged particles. It is a fundamental concept in electricity and magnetism, and is described by the electric potential, which is a scalar quantity.

## 2. How is an electric potential field created?

An electric potential field is created by the presence of charged particles, such as electrons and protons. When these charged particles are in close proximity, they create a force field that can act on other charged particles in the vicinity. This force field is known as the electric potential field.

## 3. What is the relationship between electric potential and electric field?

Electric potential and electric field are closely related concepts. The electric potential is the amount of work required to move a unit charge from one point to another in an electric field. In other words, it is the potential energy per unit charge. Electric field, on the other hand, is the force per unit charge experienced by a charged particle in an electric field. They are inversely proportional to each other, with the electric field being the negative gradient of the electric potential.

## 4. How does an electric potential field affect the behavior of charged particles?

The presence of an electric potential field can affect the behavior of charged particles in several ways. First, it can cause a charged particle to experience a force and move in a certain direction. Second, it can cause a charged particle to accelerate or decelerate depending on the direction of the electric field. Finally, it can also determine the amount of potential energy a charged particle has at a certain point in space.

## 5. Can electric potential fields exist without the presence of electric charges?

No, electric potential fields cannot exist without the presence of electric charges. The electric potential is a result of the presence of charged particles and their interactions with each other. Without any charged particles, there would be no electric potential field. However, there can be regions in space where the electric potential is constant, known as equipotential surfaces, even in the absence of charged particles.

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