Phys 15b: Lab 0: Parts Checkout 1January 31, 2007Experiment 0: Parts Checkout, Physics 15bCheck out your kit by Friday, Feb. 9, 20071 Buying a Lab KitYou’ll need a check for $80 (to Harvard University). Our lab TF’s will preside in roomSC305, Tuesday through Thursday evenings, February 6, 7, 8, 6:30 to 7:30 p.m.If you miss all those chances, then show up on Friday afternoon, February 9, 5-6 p.m.A Non-lab?You will NOT have to turn in your lab book, after doing this “experiment”—which isnot really an “experiment” at all, but only a chance to confirm that your box of tools andparts is complete and functional, and then—to keep you from getting totally bored—a littlesoldering exercise. In the process you will gain a little familiarity with some of the items.If there are any parts missing, or if the meter, transformer, or soldering iron do not workproperly, come to the help lab, Room 305 in the Science Center. Members of the lab staffwill be there Friday, February 9, 5-6 p.m.Note: The lab kits are not returnable. We regret this policy, but we can’t changeit. So please be sure you want to take the course, before buying your kit. Since this “Lab0” doesn’t ask much of you, you should have more than a week to make up your mind beforeyou commit yourself by buying the kit.Procedure:1. Parts checkVerify that every item on the tools and parts list attached to this write-up is present in yourtoolkit. Find some space to lay the larger things out so you can be sure all are in order.If a part is missing, don’t panic; just make a note of the part, and next time you come tohelp lab pick up the missing part.2. Meter check.Read the instruction booklet for your meter. Follow the directions on page 9 of the book toinstall the battery. The small flathead screwdriver should work in the phillips head screw atthe back of the meter. Install an AA battery and notice your meter’s fuse (small gray cylin-der with metal caps); you have a spare one to replace it if it blows. Carefully zero the red(AC) and black (DC) meter scales. This is done by adjusting the clear plastic screw locatedPhys 15b: Lab 0: Parts Checkout 2in the center bottom of the display window. (What is the mirror on the display window for?)Before you do this next step take time to think about what the different test probe portsare for and why there are two sets of them. This is important.Plug in the test probes and read the voltage of one of your new AA cells with your meter,using a scale appropriate for 1.5 volts. Touch one meter probe to each end of the battery,the positive probe to the button. Record the voltage in your notebook as precisely as youcan. Interpolate within a small division, using the mirror scale to eliminate parallax (moveyour head until the needle is on top of its mirror image).Check the zero of the ohms scales on your meter by touching the ends of the test probes toeach other. Make sure you make good contact. You should be able to set zero on all scaleswith the red adjusting wheel.Note the OFF position on the meter. If the probes touch for a long time while on theohms scale, the internal battery will run down. To avoid this (annoying) possibility, it isbest to get into the habit of always turning off your meter after each use.3. Transformer check.Unpack the 12V/2A transformer. Peel the two conductors apart for a length of about2 inches.Examine your extension cord, and, if it has sockets that turn to close, open them (usingthe prongs of the plug at the other end of the cord makes this maneuver). Then plug thecord into an outlet convenient to your work space. Bend the two transformer wires apartsothey won’t accidentally touch each other, and keep any conductor from connecting betweenthem, such as a metal table top. Why be careful about this? In electrical jargon the twoends of the wires coming from the transformer are called leads (sounds like Leeds). Plugthe transformer into the extension cord. Set your meter on an AC scale appropriate formeasuring roughly 12 volts and make contact between a probe and each output wire inorder to measure the output voltage. Make good contact between the lead and test probeby using the probe tip to push the lead down against the top of your (insulating) workbench(a wood desk or pad of paper will work fine). (This procedure of measuring the voltage ofan unknown source without touching with your fingers is very important. Never assumethat a device is operating properly, safely check the voltage first!) Record your result. Thevoltage should read around 12 volts. If it reads higher than 20 volts unplug the transformerand notify us. 12 volts is a low enough voltage that you can touch the conducting leadswith your fingers. The electrical resistance of your fingers is high enough so that very littlecurrent will pass. What happens when your meter is set for d.c. volts? Unplug the trans-former when you are finished.4. Soldering iron check.Phys 15b: Lab 0: Parts Checkout 3(We plan to show the famous 15b soldering video probably Tuesday, February 6. Thismay come after you have done some experimenting on your own. That’s OK: your ex-periments may help you appreciate the skilled soldering you’ll see. Tom Hayes will try toperform a don’t demo that same day: showing some really ugly soldering technique.)Unpack your soldering iron and bend up the central support of the stand. Take your sp ongewhile it’s still dry and trim the corners with the scissors so that it fits snugly into the plasticdish. Dampen it with tap water. When soldering, you should work on a manila folder, apiece of cardboard, or a similar table-covering to protect your desk from any molten solder(or the hot iron itself). The iron does not get hot enough to ignite ordinary materials likepaper, wood, or carp et, but it will char them. Place your iron on its stand, and beforeplugging it into the extension cord arrange things to minimize the chance that you, or any-thing else, will come in contact with the part of the iron that projects from the handle.It all gets hot, not just the tip. Also, avoid a situation where a tug on the extension cordwill cause the iron to fall to the floor.The tip of the iron needs to be tinned (coated with solder). Otherwise it will oxidizeand be useless for soldering. For the initial tinning it is imp ortant to melt solder generouslyonto the whole tip as soon as it gets hot enough to melt the solder. When the solder meltsyou will smell the rosin flux which is a blend of