# How Do You Calculate Magnetic Field Strength at Different Points?

• BuBbLeS01
In summary: They should all be pointing into the page or out of the page. You're thinking of the direction of the current, but you need to be thinking of the direction of the magnetic field that the current creates.In summary, the conversation discusses how to calculate the magnetic field strength at three different points (a, b, and c) using Ampere's Law and the Biot-Savart Law. The speaker also asks for clarification on why the field at point b is found by adding the contributions from both wires rather than subtracting them. The expert advises the speaker to follow the rules of the forum and show all steps and relevant equations in order to identify any mistakes. The expert also provides a hint that the direction of the magnetic
BuBbLeS01

## Homework Statement

What is the magnetic field strength at point a? (a=2.25 cm, b=5.14 cm, I=15 A.)
What is the magnetic field strength at point b?
What is the magnetic field strength at point c?

## The Attempt at a Solution

So we understand how to get the magnetic field strength at a and c...B2 - B1...but why for the magnetic field at point b do we add them?

hm ... shouldn't those be "point 1", "point 2", and "point 3"?

Anyway, yes, the magnetic field is a vector field, so you can use vector addition to add up the contributions from all the sources of the field. You are already doing this when you use Ampere's Law, since you're adding the contributions from all the little infinitesimal current elements along the wire.

Show us what you've got, and we'll let you know if it's okay.

I know that you need to add the vectors but since B1 points to the left its X component is negative shouldn't you minus that from B2? And it make it equal 0?

9.274e^-5 T
0.0002 T
9.274e^-5 T

Also, did you really copy this problem correctly and in its entirety? I find it odd that the points are referred to as "a, b, and c", where the diagram shows those as distances. Also, b appears to be the distance between the two wires, so we don't know where point 2 is located ... is it supposed to be at the midpoint between the wires?

B1 = UI/2*pi*a = 1.334e^-4
B2 = UI/2*pi*(a+b) = 4.061e^-5
B2-B1 = 9.279e^-5

Thats for point 1 and point 3

Point 2...
B1 = UI/2*pi*.5B = 1.168e^-4
B2 = same
B1+B2 = 2.335e^-4
Why add them and not subtract them because B1 points to the left and B2 points to the right so wouldn't it be -B1 + B2 = 0

I'm sorry, I'm really not following your reasoning. It would really help if you'd follow the rules of the forum and state the relevant equations as well as showing all your steps.

What is UI? Why are there no vectors? Why do you say that B1 points to the left and B2 to the right?

I think if you work this through step by step, then either you will catch where you've made a mistake or someone here will identify it for you. You should start with Ampere's Law and the Biot-Savart Law, paying particular attention to the direction of the B field. There are no components of B pointing to the left or to the right in this problem, and the field at point 2 is not zero.

UI = u0*I, where u0 = magnetic permeability (probably of free space) and I = current.

Thanks...I am sorry I just wanted to understand the second part of the question (point 2) but I haven't had time to sit and type everything I have so I will try to do it later.

Okay - if you do come back here before finishing this problem, though, the hint you need is that you're coming up with the wrong directions for your B vectors.

## 1. What is a magnetic field?

A magnetic field is an invisible force created by moving electric charges, such as those found in magnets or electric currents. It is the area around a magnet or electric current where its influence can be felt.

## 2. How is a magnetic field created?

A magnetic field is created by the movement of electric charges, either through a current or the alignment of particles in a magnet. In physics, it is described by the movement of charged particles, specifically their motion and orientation.

## 3. What are the properties of a magnetic field?

A magnetic field has two main properties: direction and strength. The direction of a magnetic field is determined by the north and south poles of a magnet, while the strength is determined by the distance between the poles and the material of the magnet.

## 4. How does a magnetic field affect objects?

A magnetic field can exert a force on objects that have a magnetic property, such as other magnets or materials with unpaired electrons. This force can cause objects to move or align with the magnetic field.

## 5. How is a magnetic field measured?

The strength of a magnetic field is measured using a device called a magnetometer. This device can measure the magnetic field in units called teslas, with stronger fields having higher values. The direction of a magnetic field can also be measured using a compass, which aligns with the direction of the magnetic field lines.

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