University Physics II Lab I need a few pretty easy answers (in bold below) if an

Question

University Physics II Lab
I need a few pretty easy answers (in bold below) if anyone can help me out (any other advice on this lab would be GREATLY appreciated). I have included the entire lab but only the bolded questions I really need answers. Here are a couple factors that will help:

Our bar magnet was a cylinder about an 0.04 m in length and a radius of 0.009 m, and weighed roughly 0.08 kg (this is an estimate and I might be off by a LOT, so feel free to use your own intuiton or understanding on any of this, I'm giving pretty much all estimates and accuracy is not of the utmost importance in the exact dipole moment, just something relatively close). I also bolded the equation we are to use.

EXEM09 Force on a Current Carrying Wire Objectives
You should have read Section 20.2 of the Matter & Interactions 4e textbook before beginning this experiment.
After completing this activity you should be able to:
• Predict and observe the magnetic force on a current-carrying wire
• Use the magnetic force to obtain a rough measurement of a bar magnet’s dipole moment

1 Purpose Current carrying wires will experience forces when placed in regions of magnetic field. In this lab experiment, you will explore the directions of the forces on a current carrying wire as well as make a rough measurement of the magnetic dipole moment of a bar magnet. 2 Directions of the force Record all your measurements clearly in your notes. 1. Prepare an insulated wire 1 or 2 meters long so that you can “hang” a section of straight wire over the edge of the table. The section of straight wire should hang so that it is parallel to the floor, as shown in Figure 1 Figure 1: A diagram of the circuit using the long insulated wire and two batteries. 2. Connect the long insulated wire two two batteries using connecting wires with alligator clips and a battery holder. Since there is very little resistance in this circuit, only leave the circuit connected for a short time while you are making measurements and/or observations. 3. Use the magnet to deflect the straight section of the wire. Consider the following: (a) How would you orient the magnet so that the straight section of the wire is deflected in a direction toward the table? Is this the only way to position the magnet to get this result? (b) How would you orient the magnet so that the straight section of the wire is deflected in a direction away from the the table? Is this the only way to position the magnet to get this result?

3 A rough measurement of the magnetic dipole moment
1. Connect an ammeter into the circuit. Remember that an ammeter need to be connected in series for it to function properly.
2. Position the magnet so that the wire deflects from its original position by about 1 cm. When the wire moves by this much, we know that the force exerted on the wire by the magnetic field of the bar magnet is on the order of the gravitational force of the wire.
That is mg |I ~l × B~ |
Note: This is an approximation that we are making! We are NOT saying that the two are equivalent. If we saw the wire fly dramatically to the side, we’d know that the magnetic force was much larger than the gravitational force. Similarly, if we didn’t see the wire move at all, we’d know that the gravitational force is much larger than the magnetic force. Since we see the wire move a tiny bit, we know that these forces must be on the same order.
3. Decide what measurements need to be taken in order to determine the dipole moment of your bar magnet.
4. Make the measurements (use values at top and guess if the ones necessary are not included) and determine the dipole moment of your magnet. Compare this rough approximation with other measurements you’ve made for your bar magnet. Do the values agree with each other to an order of magnitude?

Please show the work to obtain the dipole moment with the given (or estimated) values and the equation in bold. Thank you immensely!

Explanation / Answer

The force on a current carrying wire is of the order given by I*L*B. I is the current and hence, the ammeter reading, L is the length of the wire and B is the strength of magnetic field. Now, this force is of the order of the gravitational force when the wire deflects by 1 cm, and hence is of the order of the quantity m*g. We need the mass of the wire, current in the wire, length of the wire and we can estimate the magnetic field of the bar magnet. Now, the torque that the wire experiences is equal to Magnetic Dipole Moment * Magnetic field strength. So, the weight(m*g) divided by the Magnetic field strength(B) gives us the order of the magnetic dipole moment of the bar magnet.

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