Force from a rectangular loop of wire?

• cdotter
In summary, the conversation discusses finding the forces on a rectangular loop of wire using the right hand rule and the equation F=IdL x B. The magnetic field direction can be determined by using the right hand rule, and the forces on the top and bottom segments of the loop cancel out due to their opposing directions. The left and right forces would also cancel, but the left side is closer to the straight wire and therefore experiences a force from it. The conversation also mentions the frustration of not finding this information in the textbook.
cdotter

Homework Statement

[PLAIN]http://img710.imageshack.us/img710/3483/71071851.png

n/a

The Attempt at a Solution

I understand everything except "the forces on the top and bottom segments cancel."

How do I figure out that they cancel? I understand that a force is orthogonal to both the current flow and the magnetic field...but there's no magnetic field given?

Last edited by a moderator:
Nevermind, I think I figured it out.

The direction of the magnetic field can be found by using the right hand rule. Place your thumb along the direction of current and curl your fingers around the wire.

I1's magnetic field goes into the page on the right side. It comes out of the page on the left side, but there's nothing on the left side of the page so it's inconsequential.

To find the force on the rectangular section by the straight section use the right hand rule again in accordance to F=IdL X B. That is to say, cross the length vector (which is in the same direction of I) into the magnetic field vector you just found.

Top section: Force vector points up
Right section: Force vector points right
Bottom section: Force vector points down
Left section: Force vector points left

Top and bottom cancel out. Left and right would also cancel but one side (the left) is closer to the straight wire, which happens to be exerting a force on the loop.
It's sad that it took me an hour of searching Google to explain something so simple that I couldn't find in my textbook...I hate textbooks so much.

1. What is the formula for calculating the force from a rectangular loop of wire?

The formula for calculating the force from a rectangular loop of wire is F = I * L * B, where F is the force in newtons, I is the current in amperes, L is the length of the wire in meters, and B is the magnetic field strength in teslas.

2. How does the direction of the current affect the force from a rectangular loop of wire?

The direction of the current determines the direction of the force from a rectangular loop of wire. If the current is flowing clockwise, the force will be upwards, and if the current is flowing counterclockwise, the force will be downwards. This is known as the right-hand rule.

3. Can the force from a rectangular loop of wire be increased?

Yes, the force from a rectangular loop of wire can be increased by increasing the current, the length of the wire, or the magnetic field strength. The force is directly proportional to each of these variables.

4. What is the direction of the force on a rectangular loop of wire in a uniform magnetic field?

The direction of the force on a rectangular loop of wire in a uniform magnetic field is perpendicular to both the direction of the current and the direction of the magnetic field. This means that the force will be either upwards or downwards, depending on the direction of the current.

5. What is the relationship between the force from a rectangular loop of wire and the area of the loop?

The force from a rectangular loop of wire is directly proportional to the area of the loop. This means that if the area of the loop is doubled, the force will also double. This relationship is known as the area law.

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