# Measuring earth magnetic field strength

1. Mar 16, 2013

### ry2ncz

I'm somewhere at a suburb near Sydney and I have problems designing an experiment to measure the strength of the earth magnetic field so that means now I'm close to geographic south and I'm close to magnetic north right? how do I measure the angles between the GS and Mn and what do I have to look for before measuring the strength of the earth magnetic field.... I have power supply, dip needle, a compass, ammeter , resistor and connecting leads and a ruler to measure the distance of what?

2. Mar 16, 2013

### ry2ncz

And I am a year twelve students also having difficulty to understand earth magnetic field I mean the lines of the magnetic

3. Mar 16, 2013

### davenn

hi there
welcome to PF
I am also from Sydney :)

A magentometer is the usual device for measuring the earth's magnetic field.
These can be built are reasonably low cost prob <\$50. There's a lot of amateur scientists around the world that use a magnetometer to measure fluctuations in the field strength.
A reasonable fluctuation occurred just within the last 24 hours after a flare on the sun and a CME ( coronal mass ejection). When these CME's hit the Earth's magnetic field it causes the field to compress and then expand again ... its that that the magnetometer picks up

do a google search on fluxgate magnetometer
there's many links to info and circuits etc :)

Dave

4. Mar 16, 2013

### ry2ncz

Sorry daven the magnetometer is bow provided to measure the earths magnetic field strength And I don't really understand the figure shown in 56785.... I have learnt about magnetic field but I couldn't understand much of the vocab because I'm my English level is not that good.... I hope I have not offended u mate

5. Mar 16, 2013

### ry2ncz

Not*

6. Mar 16, 2013

### xAxis

Do you understand what vectors are, and how we represent the magnetic field?

7. Mar 16, 2013

### ry2ncz

I understand what vectors are but I do not how to represent in magnetic field I got a bit confuse at that point

8. Mar 17, 2013

### xAxis

Magnetic field is vector field, but is best represented as lines of force. At every point the magnetic field is tangential vector to the line et that point. You must check on the internet what those look like for the earth, it's easy to find. Then it shouldn't be difficult to visualise why is inclination in your book 0 degrees (parallel) at equator and why it is perpendicular to the pole. You should at that point have some ideas how to solve your problem.

9. Mar 17, 2013

### ry2ncz

xAxis, that's not 0 degree I think it represents something else but I just couldn't figure it out what it is

10. Mar 17, 2013

### xAxis

"It varies from 0 degrees at the equator to 90 degrees at the pole".
This is citation from your book. Have you checked the picture of the magnetic force field of the earth? Or of the bar magnet as they are similar?

11. Mar 17, 2013

### Ryoko

I think the goal from the text is to have you build a current loop and introduce a known current into it. If you know the size of the loop, the number of turns, and how much current is running through it, you can determine it's magnetic field strength in the center. The idea then is to make a loop, place the compass in the middle, and apply a current so that the magnetic field in the loop just cancels the earth's magnetic field.

12. Mar 17, 2013

### ry2ncz

xAxis that is why I don't understand.... Maybe I will check with my classmate today I know the inclination and declination of my town now but I have no idea putting the vectors together. What I mean is that what do I have to find out first before looking for the value for earth magnetic field

13. Mar 17, 2013

### ry2ncz

What formula do I have to know for this.... My teacher told me that I have to make a comparison of F/L=I1I2/d (Mo/2pi) I have totally lost what he really wants here I show u second page of that paper and the formula

14. Mar 17, 2013

### xAxis

He wants you to know the relation between the current and the magnetic field around the wire generated by it. You have to understand it in order to do your task, as well as the shape of the magnetic field of the earth.
That formula is the force per unit lenght between to parallel wires when there is a current in them.

15. Mar 17, 2013

### ry2ncz

Okay xAxis I'll try to work it out..... I hope I can understand what I want to find as well thx agn axis for having patience