Electric field line diagrams showing correct and incorrect patterns for different charge arrangements.

Let's go through each question on the Electric Field Lines Worksheet and solve them step by step with explanations.

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Question 1: Which of these electric field line patterns are incorrect? Explain what is wrong.

We are given five diagrams (A to E), each showing a central charge with electric field lines.

#### Rules for Electric Field Lines:
1. Field lines start on positive charges and end on negative charges.
2. Lines never cross.
3. Lines are closer together where the field is stronger.
4. For a single point charge, field lines should be radially symmetric (pointing outward for +, inward for –).
5. The number of lines is proportional to the magnitude of the charge.

Now let’s analyze each diagram:

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#### Diagram A:
- A positive charge (+) in the center.
- Field lines radiate outward in all directions.
✔ Correct — this matches the expected pattern for a positive point charge.

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#### Diagram B:
- A negative charge (–) in the center.
- Field lines point inward toward the charge.
✔ Correct — this is correct for a negative point charge.

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#### Diagram C:
- A positive charge (+) in the center.
- Field lines point inward (toward the charge).
✘ Incorrect — field lines should point away from a positive charge, not toward it. This is backwards.

> ✔ Error: Field lines should originate from positive charges, not terminate on them.

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#### Diagram D:
- A positive charge (+) in the center.
- Field lines radiate outward, but they start from the charge and curve inward or seem to intersect near the charge.
- Also, some lines appear to cross or loop back.
✘ Incorrect — field lines must be smooth and non-crossing. In a single point charge, lines must be straight and radial. Curved or intersecting lines suggest an error.

> ✔ Error: Field lines cannot cross, and for a single point charge, they should be straight and radially symmetric. The curved/intersecting lines here violate these rules.

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#### Diagram E:
- A negative charge (–) in the center.
- Field lines point inward, but there is a gap in the pattern (e.g., missing lines in one direction).
✘ Incorrect — field lines should be symmetric and evenly distributed around a point charge. Missing lines or uneven spacing suggests an incomplete or inaccurate representation.

> ✔ Error: Field lines must be uniformly distributed around a point charge due to spherical symmetry. Asymmetry or missing lines are unphysical.

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#### ✔ Summary for Question 1:
Incorrect diagrams: C, D, and E

- C: Field lines point *into* a positive charge — should point *outward*.
- D: Field lines are curved and crossing, violating field line rules.
- E: Field lines are asymmetric and missing in some directions — violates radial symmetry.

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Question 2: Mr. Vo drew electric field lines for two charges. What did he do wrong?

The diagram shows two positive charges (+), with field lines:
- Starting from each charge,
- But some lines connect the two charges, curving between them and ending at the other charge.

This is incorrect.

#### Why?

- Field lines originate from positive charges and terminate on negative charges.
- Since both charges are positive, no field line can end on another positive charge.
- Field lines must either extend to infinity or connect to a negative charge.
- Here, field lines appear to go from one + to another +, which is not allowed.

> ✔ Error: Field lines cannot connect two positive charges because there is no negative charge to terminate them. The field lines should repel each other and diverge, not converge between like charges.

✔️ Correct behavior: Field lines from two like charges (both +) repel and curve away from each other, never connecting.

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Question 3: From the diagram, object A is ___ and object B is ___.

We see a field line pattern where:
- Field lines enter object A (arrows pointing into A),
- Field lines exit object B (arrows pointing out of B).

Also, the field lines curve from B to A, indicating a flow from B → A.

#### Recall:
- Field lines start on positive charges and end on negative charges.
- So if lines enter A, then A must be negative.
- If lines leave B, then B must be positive.

So:
- Object A is negative (–)
- Object B is positive (+)

> ✔ Answer: Object A is negative, and object B is positive.

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✔ Final Answers:

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1. Incorrect diagrams: C, D, E

- C: Field lines point into a positive charge — should point out.
- D: Field lines cross and are not radial — violates symmetry and non-crossing rule.
- E: Field lines are asymmetric and missing — violates uniform radial distribution.

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2. Mr. Vo’s mistake:
He drew field lines connecting two positive charges, which is incorrect. Field lines cannot end on a positive charge unless there's a negative charge. For two like charges, field lines should diverge and not connect; they should repel each other.

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3. Object A is negative, and object B is positive.

Because field lines enter A (negative) and exit B (positive).

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