Here is a magnets. It has north pole and south pole. We use a small compass to feel the magnetism, and draw the magnetic lines on board.
Magnetic lines drift away from North pole, while south pole attracts magnetic lines. Lines go from north to south.
These are the magnetic lines
This is an oscilloscope. By moving the magnets on top of the machine, we observe the pattern change
We conclude that there exists magnetic field. which causes the change in oscilloscope.
How to determine the direction of the B(magnetic field) and electrical force?
Use right-hand rule if it is positive charge; use left-hand rule if it is negative charge
If magnetic is parallel to beam, F net=0
We know F=qvB(cross product)=qvBsin(theta) Apply it in the folloeing problem
Place a wire loop floating above the magnet in E,W direction. What will happen if turn on the generator?
The loop will turn 90 degree and stop.
This move is due to the torque on loop.
torque=r x F
F=IL x B
torqur=r IL sin(@)(sin@)=rILpsin^2@
MAGNETIC FORCES ON A SEMICIRCULAR WIRE
Consider the length of current-carrying wire with a semicircular kink in it shown below. Predicting and calculating the force on the wire when placed in a magnetic field is good practice in the use of physical reasoning about the action of the Lorentz force and the use of the spreadsheet to do numerical calculations. You’ll need to use the equation you derived previously for your calculations.
b. Use the equation you derived in previously. Break the wire into at least 15 segments and perform a numerical calculation of the net force on the wire using the spreadsheet. (Your spreadsheet should look like the following sample.) Assume that B = 10.0 teslas over the region, I = 0.5 A in a counterclockwise direction. Suppose the radius of the semicircular kink is given by R = 7.0 cm. Plot the force on each segment of wire as a function of the segment number. Why is the force much smaller for some segments than for other segments? Affix your printouts in the following space.
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