Right-Hand Rule in Physics | Overview & Examples - Lesson | Study.com - Free Printable

The image illustrates the magnetic field produced around a straight current-carrying wire, using the right-hand rule. Let's break down the physics and explain the solution.

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🔹 What is happening in the image?

- A straight wire carries an electric current (I), shown by the red arrow.
- The magnetic field (B) generated by this current forms concentric circles around the wire.
- The direction of the magnetic field is determined using the right-hand rule.

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🔹 Right-Hand Rule for a Straight Wire

To find the direction of the magnetic field:

1. Point your right thumb in the direction of the conventional current (I) (from positive to negative).
2. Curl your fingers around the wire.
3. The direction your fingers curl gives the direction of the magnetic field (B).

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🔹 Analysis of the Two Cases in the Image

#### ✔ Left Side:
- Current flows upward (thumb pointing up).
- Fingers curl counterclockwise when viewed from above.
- Magnetic field lines form concentric circles around the wire.
- The blue arrows show the direction of B, which is counterclockwise around the wire.

#### ✔ Right Side:
- Current again flows upward (thumb up).
- The hand grips the wire, and fingers curl clockwise when viewed from above?
- Wait! This seems inconsistent at first glance.

But wait — look carefully:
In the right diagram, the wire is perpendicular to the plane, and the view is top-down. The magnetic field lines are circular and clockwise as drawn.

⚠️ That’s a problem — it contradicts the right-hand rule!

Let’s double-check:

- If current is upward, thumb points up.
- Fingers curl counterclockwise when viewed from above.
- So, the magnetic field should be counterclockwise, not clockwise.

But in the right diagram, the field lines are drawn clockwise.

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✘ Error in the Diagram?

Yes — there appears to be a mistake in the right-hand side illustration.

If the current is upward (as shown), then:

- The magnetic field should be counterclockwise when viewed from above.
- But the drawing shows clockwise field lines.

This would only be correct if the current were downward.

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✔ Correct Interpretation

Let’s fix it:

| Case | Current Direction | Magnetic Field Direction |
|------|-------------------|--------------------------|
| Left | Upward → Thumb up | Counterclockwise (fingers curl) |
| Right | Upward → Thumb up | Should be counterclockwise (not clockwise) |

So, the right diagram has an error: the magnetic field direction is wrong.

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🧠 Summary & Solution

Problem: Determine the direction of the magnetic field around a straight wire carrying current.

Solution:

Use the right-hand rule:
- Point your thumb in the direction of the current.
- Curl your fingers around the wire.
- Your fingers show the direction of the magnetic field.

For upward current:
- Magnetic field lines are concentric circles.
- Direction: Counterclockwise when viewed from above.

✔ The left diagram is correct.
✘ The right diagram is incorrect — it shows clockwise field lines for upward current, which violates the right-hand rule.

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✔ Final Answer:

> The magnetic field around a straight current-carrying wire forms concentric circles whose direction is given by the right-hand rule. For an upward current, the magnetic field is counterclockwise when viewed from above. Therefore, the left diagram is correct, while the right diagram incorrectly shows clockwise field lines.

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Let me know if you'd like a corrected version of the diagram or want to explore solenoids or loops next!