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Determination of Horizontal Component of Earth's Magnetic Field

Here's the background of our experiment.

Purpose: In this experiment you will use a current-carrying loop to determine the horizontal component of the earths magnetic field for our locality. (Massachusetts, USA)

Apparatus:
1. Circular conducting loop
2. Compass
3. Power supply and powersate
4. Ammeter
5. Wires

Theory:
The earths magnetic field varies in strength and direction from place to place on its surface. At our locality, the field has a direction that can be expressed with a vertical and a horizontal components. The direction of the horizontal component can be determined using a compass placed in a way that the needle is able to rotate freely in the horizontal plane.

We used a formula B1=uo/NI/2r

Procedure:
connect the power supply, ammeter, and the conducting loop in series. Place the conducting loop in the vertical plane, and attach the compass at the center of the loop.
Orient the conducting loop in the plane of the earths magnetic field as indicated by the compass.
Turn on the power supply and use the powerstat to control the amount of current passing ghrought the loop as indicated by the ammeter. Adjust the current to .1A - .6A.

We plotted our data on a graph setting tan0 etc...
Then we had to Calculate the horizontal compone of the earths magnetic field Bh.

The data came out as follows:
CurrentI 0(degree) Tan0
.1 25 .466
.2 45 1.0
.3 60 1.73
.4 70 2.75
.5 73 3.27
.6 80 5.67

The we calculate our slope and it came out to be:
m= 8.75

Then we calculated the Bh field, which came out to be:
Bh = 1.45 x 10^-5

There are 3 questions I can not answer on the lab, I hope some one can help me here.

1. Is the magnetic plane also the meridian plane in our Lab room?
I looked up the definition of meridian and then chose to answer yes but I don't know if I am right or if I should answer yes to this question.

2. Based on the idea of our lab, can you think of a method tht will allow us to compute the strength and direction of the earths magnetic field for our locality? Explain your idea.

Well I am assuming that this idea should have synonomous equipment to the experiments apparatus, but I am lost on how to explain or how to do this.

3. Do your experimental value of the horizontal component of the earths magnetic field agree with athe accepted value for our locality? What physical arrangements in our lab room mahy count for some of the difference?

I tried to go on the internet and locate a map of the earths magnetic fields to see if the Bh value we calculated matched up for this part of the earth but i couldn't find one.

Solution Preview

1.) Yes! You are correct provided there is no other magnet or magnetic field nearby your experiment table. If there is some magnetic filed nearby the setup, definitely that will change your plane as well as value of Bh.
<br>Basically your experiment is based on Tangent Law, in which one external field (earth magnetic field) and field due to current carrying coil, you are using, should be perpendicular to one another,i.e in the beginning of your experiment the magnetic needle should lie in the plane of coil and when you pass ...

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