Electric fields around charged objects

1. Definition of an Electric Field

• An electric field is a region where an electric charge experiences a force.
• It is a vector quantity, meaning it has both magnitude and direction.
• Field lines show the direction a positive test charge would move if placed in the field.

2. Properties of Electric Field Lines

✔ Start and end perpendicular to the surface of a charged object.

✔ Never cross each other.

✔ Closer where the field is stronger.

✔ Directed from positive to negative.

3. Representing Electric Fields

a) Around a Positive Point Charge

• Field lines radiate outward (away from the charge).

b) Around a Negative Point Charge

• Field lines point inward (towards the charge).

c) Between Two Like Charges (Both Positive or Both Negative)

• Field lines curve outward, showing repulsion.
• If the charges are equal in magnitude, the field is symmetrical.

d) Between Two Like Charges of Unequal Magnitude

• Field lines are denser near the stronger charge, indicating a stronger field.

e) Between Two Opposite Charges (Positive and Negative)

• Field lines curve from the positive to the negative charge.
• The field is strongest between the two charges.

f) Between Two Oppositely Charged Parallel Plates

• The field is uniform (equally strong everywhere).
• Field lines are straight, parallel, and evenly spaced.

4. Key Takeaways

✔ Electric fields exert forces on charges.

✔ Field lines always move away from positive and towards negative charges.

✔ Stronger fields have closer field lines.

✔ Parallel plates create a uniform electric field.

Exam Tip

💡 When drawing electric field diagrams, always ensure arrows point in the correct direction!