magnetometer in a bottle - university of leicesterpage%2%of4% % whatequipmentdoyouneed? % r...

of 4

Magnetometer in a bottle

What is a magnetometer? A magnetometer is an instrument that measures changes in a magnetic field. Magnetometers are used to measure changes in magnetic fields. They are used in many devices from mobile phones to satellites. Scientists also use magnetometers to measure the changes in the Earth’s magnetic field that occur due to the influences of the solar wind as it pushes up against the Earth’s magnetosphere. Scientists use magnetometers placed at many different places around the Earth to measure these changes. The data from the magnetometers is often gathered together to calculate what are known as magnetic activity indices. By looking at disturbances to the Earth’s field, it is possible to know that much is happening in the Earth’s magnetosphere, even though the aurora might not be visible at that moment.

This graph shows how the activity in the UK can change during one day. Note how the graph suddenly changes around 20:00. We will make a magnetometer to measure deviations in the Earth’s field. Credit: AuroraWatch UK

This image shows the Earth’s magnetosheath. The lines show the magnetic field lines around the Earth and those in the solar wind (the Interplanetary Magnetic Field). The outer boundary of the Earth’s magnetosphere, the magnetopause, moves in and out all the time in response to the solar wind. Credit: NASA/Goddard/Aaron Kaase

of 4

What equipment do you need? -‐ A 2 litre clear plastic bottle, cleaned and any labels removed -‐ Some sand (to fill about a quarter of the bottle) -‐ A sewing needle -‐ A craft knife and a pair of scissors -‐ One small bar magnet (this must be able to fit horizontally in the bottle) -‐ Thread -‐ Clear tape and/or Blu-‐Tack -‐ Superglue -‐ Normal glue -‐ A small piece of card -‐ A plastic drinking straw -‐ A table lamp with a flexible head and a clear unfrosted bulb -‐ A small mirror, silver sequin or highly reflective card -‐ A piece of white paper -‐ A ruler -‐ Pen and paper for recording the results

Make your magnetometer -‐ Using the sewing needle, make a small hole in the lid of the bottle, replace the lid on

the bottle -‐ Using the craft knife, cut the bottle into two, with the cut made a third of the way from

the top -‐ Place some sand in the bottom part of the bottle, this is to make the bottle more

stable -‐ Stick the bar magnet to the top middle of a small piece of card -‐ Stick a small piece of highly reflective card (or the small mirror or the silver sequin) to

the middle of the bar magnet card -‐ Cut off a piece of the drinking straw about 2 to 3 cm in length and stick this on top of

the magnet, in the middle -‐ Thread some thread through the piece of straw and tie to make a roughly triangular

loop with sides about 5 cm in length -‐ Tie this loop to another thread that is then passed through the hole in the lid, and

secure this thread with some Blu-‐Tack or tape -‐ Replace the upper part of the bottle to the bottle part, securing the top with Blu-‐Tack

or tape -‐ The magnet and card should now hang inside the bottle without touching the sides

and so the mirror is not level with the seam that was cut earlier – this is your magnetometer

-‐ Position the lamp and magnetometer so that a spot of light as reflected off the magnetometer mirror is seen on a wall about 1 m away

-‐ Draw a guide line with some distance markings on a piece of paper -‐ Fasten the piece of paper with the guide line on the wall where the spot is found, so

that the spot is roughly in the centre position of the guide line -‐ BE CAREFUL USING THE GLUE AND CRAFT KNIFE

of 4

Compare your data! Compare your data to what is happening in the aurora: spaceweather.com aurorawatch.lancs.ac.uk Compare your results to other people’s results in your group. Let me know about your experiment: [email protected]

Things to consider when you take your measurements You may want to record the ambient conditions when you take your measurements, and note these down with your results. For example; -‐ Is there any lightning going on when you are taking measurements? -‐ Is there a lot of traffic nearby? -‐ What other sources of uncertainty are there? (For example, try moving a large handful

of iron objects near the magnetometer and see what happens) Remember to keep the magnetometer still during the experiment. If it gets knocked by mistake, don’t worry, but make a note of this in the comments column in your results.

Taking measurements The measurement you make is how much the spot on the wall (that reflects off the magnet) moves at certain times. You need to mark the reference position of the spot at the beginning of the experiment. The spot might not be a perfect circle, but get accustomed to the size and shape of the spot so you can measure how much the spot moves if it is very diffuse (e.g. note how much the edge or brightest part of the spot moves). Make a table of results with time in one column, and the distance the spot moves in another. Make an extra column for any other observations or notes you want to make (see the comments in ‘Things to consider’ below). At a series of times you note how much the spot has moved.

of 4

Example magnetometer in a bottle results sheet Name and location of the magnetometer: _________________________________ The size and shape of the spot: __________________________________________ The distance from my magnetometer to the wall: ___________________________

Day Date Time Deflection of spot (cm)

Notes (e.g. weather, traffic, magnetometer was disturbed, solar wind conditions as noted from a reference web page)

1 09:00

1 10:00

1 11:00

1 12:00

1 13:00

1 14:00

2 09:00

2 10:00

2 11:00

2 12:00

2 13:00

2 14:00

3 09:00

3 10:00

3 11:00

3 12:00

3 13:00

3 14:00

magnetometer in a bottle - university of leicesterpage%2%of4% % what*equipment*do*youneed?* % r...

Documents

magnetometer in a bottle - university of leicesterpage%2%of4% % whatequipmentdoyouneed? % r...