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# Chapter 25: Electric Potential

In mechanics there were two basic ways to approach problems, from the point of view of forces or energy. The same is true in electrostatics, but instead of forces and potential energy, we generally use electric fields (force/charge) and electric potentials (potential energy/charge). As before, the change in a potential energy is the negative of the work required to move an object (in this case a charged object). Instead of an electric field (a vector), we talk about the electric potential (a scalar). The electric potential is measured in Volts and, as with potential energy, the point of zero electric potential is arbitrary. Common conventions are to call Earth (and any conductors connected to Earth) zero Volts or to set the zero of electric potential at a distance very far away (infinity) from the charge distribution.

# Table of Contents

## Illustrations

- Illustration 25.1: Energy and Voltage.
- Illustration 25.2: Work and Equipotentials.
- Illustration 25.3: Electric Potential of Charged Spheres.
- Illustration 25.4: Conservative Forces.

## Explorations

- Exploration 25.1: Investigate Equipotential Lines.
- Exploration 25.2: Electric Field Lines and Equipotentials.
- Exploration 25.3: Electric Potential around Conductors.
- Exploration 25.4: Time-of-Flight Mass Spectrometer.
- Exploration 25.5: Spherical Conductor and Insulator.

## Problems

- Problem 25.1: Change of electric potential in a uniform field.
- Problem 25.2: Find the work done.
- Problem 25.3: Rank the work done.
- Problem 25.4: Determine the unknown charge.
- Problem 25.5: Find mass of particle.
- Problem 25.6: Draw the electric potential vs. x graph.
- Problem 25.7: Determine the motion in a region of electric potential.
- Problem 25.8: Ranking fields and voltages.
- Problem 25.9: Develop equation for voltage.
- Problem 25.10: Find unknown charge on pendulum.
- Problem 25.11: Charge on a sphere.
- Problem 25.12: Cylindrical or spherical symmetry?