Chapter 19: Electric Fields

Electric Field (E)

A region of space that exerts an electric force on a charged object.

Lines of Force

• Developed by Faraday and Maxwell to visualize electric fields.
• Direction of lines indicates the force on a small positive charge.
• Closely spaced lines represent strong forces; widely spaced lines represent weak forces.

Electric Field Strength

The force per unit charge, calculated using Coulomb’s law: $E=\frac{F}{q}$.

Key Points

• The direction of $E$ aligns with force vectors.
• Electric field strength is analogous to gravitational field strength.
• Vector addition is used when multiple charges create an electric field.

Electric Potential

Electric Potential Energy (U_e)

The mechanical work needed to move a charge from zero potential energy to a specific location.

Electric Potential (V)

The work per unit charge to move a charge to a specific location, measured in volts (V).

Example Problems

Example 19-1

Calculate the electric field strength for a force of 0.26 N on a test charge of 0.78 μC.

Example 19-2

Determine the field strength at a point influenced by two charges and calculate the force on a 0.75 nC charge.

Questions for Students

1. Define electric field and explain its properties.
2. Describe the relationship between electric potential energy and electric potential.
3. Use vector addition to find the net electric field at a point influenced by multiple charges.
4. Explain the concept of lines of force and their significance.
5. Solve an example problem involving electric potential and electric field strength.