Cartesian Coordinates and Cross Product of Vectors for Magnetic Field Direction?

In summary, the conversation discusses the direction of the positive z-axis for a cross product of unit vectors in a Cartesian coordinate system using the right-hand rule. It is mentioned that the positive z direction points out of the page and that the corkscrew rule can be used to determine the direction. There is also a question about the impact of the distance b on the combined magnetic field when considering two wires and a negative charge.
  • #1
The black vegetable
22
0

Homework Statement


upload_2017-2-10_15-9-0.png


Homework Equations

The Attempt at a Solution


upload_2017-2-10_15-10-26.png


the answer given is the same but without the negative sign, I don't understand because the crossproduct of unit vectors
upload_2017-2-10_15-13-41.png

when using a Cartesian coordinates of the directions given by the right-hand rule? Is the positive z direction pointing out of the page if X and Y are as follows
upload_2017-2-10_15-18-3.png

apologies if this is in the wrong section, thanks for any help in advance
 
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  • #2
Yes. ##\hat {k} = \hat {\bf \imath } \times\hat {\bf \jmath}## , so z points towards you, out of the screen.

Corkscrew rule I call it. Turn ##\hat{\bf \imath }## over the smallest angle towards ##\hat {k}##. Corkscrew will go in the minus y direction : $$\hat \imath \times\hat k = -\hat \jmath $$
 
  • #3
The problem doesn't specify which of the two wires the charge -q is a distance b from. Does the answer change if you pick the other wire to be a distance b from -q?
 
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  • #4
Thank you both your answers, TSny I thought the same, closer to the top wire the combined magnetic field would be in the opposite direction . Maybe the question is just not very good
 

1. What are Cartesian coordinates vectors?

Cartesian coordinates vectors are a mathematical representation of a point in a two or three-dimensional space. They consist of a set of numbers that describe the location of a point relative to an origin point, using a system of perpendicular lines known as the x-axis, y-axis, and z-axis.

2. How are Cartesian coordinates vectors used in science?

Cartesian coordinates vectors are used in science to describe the position and movement of objects in space. They are especially useful in physics and engineering, where they are used to calculate forces, velocities, and accelerations.

3. What is the difference between a position vector and a displacement vector?

A position vector describes the location of a point in space relative to an origin point, while a displacement vector describes the change in position of an object from one point to another. Position vectors have a fixed length and direction, while displacement vectors can vary in length and direction.

4. How do you find the magnitude of a Cartesian coordinates vector?

The magnitude of a Cartesian coordinates vector is the length of the vector, which can be calculated using the Pythagorean theorem. The magnitude is equal to the square root of the sum of the squares of the vector's components. For example, in a two-dimensional space, the magnitude of a vector (x, y) is equal to √(x² + y²).

5. Can Cartesian coordinates vectors be used in higher dimensions?

Yes, Cartesian coordinates vectors can be used in any number of dimensions. In a four-dimensional space, for example, a vector would consist of four components and would be represented as (x, y, z, t). The principles of Cartesian coordinates and vector mathematics can be extended to any number of dimensions.

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