Online Lab: Magnetic Fields Name: ll Date: l:l MW; : section; E Background: All magnets have two opposite magnetic poles: a North Pole and a South Pole. Magnets can exert forces which can either attract or repel. If two opposite poles face each other, the magnets attract (pull towards). If two of the same poles face each other. the magnets repel (pull away). Tkvo magnets create a force on each other at a distance much larger than the size of the magnets. This force can be represented by (.lrawing the magnetic field around a magnet. The magnetic field is a magnetic: force that surrounds a magnetic object at all points in space. The magnitude of the Earth's field varies over the surface of the Earth. The horizontal component of the Earth's magnetic field points toward the Magnetic North Pole (which must therefore have a South polarity), is about 50 uncrotesla on the surface of the Earth. The north end of a compass needle is attracted to the south end of the Earth's magnetic field. So the pole which is referred to as "North Magnetic Pole" is actually a south magnetic pole. Solenoid Magnet It is known that magnetism is caused by the motion of electrons. Electric currents, the ow of charged particles, are sources of magnetic elds. In a solenoid (loops of conductive wire), it is possible to generate an electromagnet, which behaves similarly to a permanent magnet made of iron. In the diagram above, the current I, ows through the solenoid. The magnetic eld produces at the central axis of the solenoid can be estimated with N B: 1 \"0.1:: () where N is the number of turns. L is the length of the solenoid. no is the permeability of free space (1.2566 x 10'10 N/A2). The second part of this lab. an electromagnetic coil (solenoid). is connected to an electric power source (battery). The battery generates current. I that runs through the coil which turns the coil into a magnet. The solenoid has a north pole (N) and a south pole (S) like a bar magnet. Developed by Melissa Butner= ETSU 1 Properties of Magnets Below there are three different interactions between two magnets. For each, indicate in the blank provided if they Attract or Repel each other. Earth's Magnetic Field 1. Label the North and South Geographic poles, and the North and South Magnetic Poles on the Diagram below. Geographic Pole Magnetic Pole |:| I;l Geographic Pole Magnetic Pole Developed by Melissa Butner= ETSU 2 Online Experiment Setup Instructions 1. Go to the following website: https://phet.colorado.edu/sims/cheerpj/faraday/latest/faraday.html?simulation=magnets-and-electromagnets 2. Click the Bar Magnet tab on the PHeT simulation. The figure below shows what you should see on your screen. 3. Use the Compass to find the direction of the magnetic field. 4. The Field Meter is used to measure the Total Magnetic Field (B), the horizontal Br and vertical components By of the magnetic field and the direction of the field expressed in degrees O. (See figure on the right.) Magnetic (B) Field Magnets and Electromagnets (2.07.01) B 0.40 G Elle Options Help BX -0.33 G Bar Magnet Electromagnet By -0.23 G Bar Magnet -145.33 0 Strength: 75 9% Flip Polarity See Inside Magnet Move me or me Show Field Show Compass Show Field Meter )Show planet Earth S N Reset All Observations 1. Drag the compass around to the bar magnet. Observe the red arrow of the compass needle. What do you notice about the needle color as you drag it around the magnet? 2. Click the Flip Polarity button in the control panel to reverse its polarity. What are the ways in which the sim reflects this polarity reversal? Developed by Melissa Butner, ETSU 3Magnetic Field Strength around the Earth 1. Click on the "Field Meter". Place the cross-hairs (+) of the meter at the point labeled A on the diagram below. Measure and Record the magnetic field B in the corresponding blank. NOTE: Don't forget to include UNITS 2. Repeat Step 1 for points B, C, D and E. A B B. C C. E. D E Observations 1. Place the compass over the United States. Which part of the compass (red is North, white is South) is attracted to the Earth's geographic North Pole? 2. Where is the magnetic field strongest? 3. As you move away from the poles what happens to the field strength? 4. Which of the magnet's poles do the red arrows point away from? 5. Which of the magnet's poles do the red arrows point toward? 6. Why do you think the red part of the compass needle always points to Earth's North Pole? Developed by Melissa Butner, ETSU7. Place the Field Meter on top of the North Pole until the direction O reads close to -90. Record the horizontal component of the magnetic field. BI = Record the vertical component of the magnetic field. By = 8. Calculate the Total Magnetic Field B using the Pythagorean Theorem. B = Magnetic Field Strength as a Function of Distance 1. Click on the "Field Meter". Place the cross-hairs (+) of the meter at the point labeled A on the diagram below. Measure and Record the magnetic field B in the corresponding blank. NOTE: Don't forget to include UNITS . 2. Repeat Step 1 for points B and C. A. B C B. C. Observations 1. Based on your data above, what do you observe about the strength of the magnetic field as you move further from Earth? Is this what you expected? Explain. Developed by Melissa Butner, ETSU 5