electro magnetic

3 WAYS TO INCREASE THE STRENGTH OF AN ELECTROMAGNET
* INCREASE NUMBER OF COILS THAT WRAP AROUND THE CORE
* INCREASE THE CURRENT FLOWING THROUGH THE COIL
* CHANGE THE CORE MATERIAL TO BEST SUIT THE ELECTROMAGNET

http://spreadsheets.google.com/ccc?key=0AhmcrnKDxOH9dDhyOXBsdlYxTU1VYWNVN0ZxekQ3eXc&hl=en

what are magnetic flux lines??

magnetic flux is a measure of the magnetic field strength existing on a two dimensional surface, such as one side of a magnet

RULES FOR FLUX LINES.

1.cant cross
2.try to shorten
3.north to south
4.cant be broken

4 things i found hard in the exam

4 things i found hard in the exam..
well everything in the exam was harder then i thourt it would be and my mind was not set on the exam.

solving resistors

If R1 = 95Ω
R2 = 62Ω,
R3 = 7Ω,
R4 = 5Ω,
R5 = 22Ω,
R6 = 68Ω,
First you add up the right side resistors becuase they are in series. so R3+R4+R5=7+5+22=34ohms.
Then you would redraw the circuit with just one resistor instead of three with the resistance 34ohms.
Then you would work out the resistance of R2 and R3 by the parallel formula 1/R1 + 1/R2 = RT
so 1/62 + 1/34 =
Then you would add up all the resistances to get the total resistance.

spreed sheet

here is my spreed sheet

here is my spread sheet

parallel circuit

Total voltage is the same as the supply voltage on every branch of the circuit.
Total Resistance = 1/R1 + 1/R2 = 1/RT
Current breaks of down the branches of the circuit then rejoins to the supply current.

series circuit

Total Resistance is the all the resistance added together. R1+R2=R3
Total Voltage adds up to the supply voltage
Total current stays the same thought out the hole circuit.

computer ergonomics: key boards and mouse

Many ergonomic problems associated with computer workstations occur in the forearm, wrist, and hand. Continuous work on the computer exposes soft tissues in these areas to repetition, awkward postures, and forceful exertions.

The following adjustments should be made to your workstation to help prevent the development of an ergonomic problem in the upper extremities:

• Adjust keyboard height so shoulders can relax and allow arms to rest at sides (an articulating keyboard tray is often necessary to accommodate proper height and distance).
• Keyboard should be close to the user to avoid excessive extended reaching.
• Forearms parallel to the floor (approximately 90 degree angle at elbow).
• Mouse should be placed adjacent to keyboard and at the same height as the keyboard (use articulating keyboard tray if necessary).
• Avoid extended and elevated reaching for keyboard and mouse. Wrist should be in neutral position (not excessively flexed or extended).
• Do not rest the hand on the mouse when you are not using it. Rest hands in your lap when not entering data.

computer ergonomics

With regard to the monitor, one must take in to consideration how the placement and maintenance of the monitor can effect both the eyes and the musculoskeletal system. The following suggestions can help prevent the development of eye strain, neck pain and shoulder fatigue while using your computer workstation:

• Make sure the surface of the viewing screen is clean.
• Adjust brightness and contrast to optimum comfort.
• Position the monitor directly in front of user to avoid excessive twisting of the neck.
• Position the monitor approx. 20-26 inches (arm's length) from user.
• Tilt top of the monitor back 10 to 20 degrees.
• Position monitors at right angles from windows to reduce glare.
• Position monitors away from direct lighting which creates excessive glare or use a glare filter over the monitor to reduce glare.
• The top of the viewing screen should be at eye level when the user is sitting in an upright position (NOTE: Bifocal wearers may need to lower monitor a couple of inches).http://www.youtube.com/watch?v=KiAR7L-LjhU