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# If two wires carry current next to each other, they will exert a force on each...

If two wires carry current next to each other, they will exert a force on each other. The force is caused by magnetic fields. One current creates a magnetic field, and this field exerts a force on the other current. The magnitude of the field created by a long, straight current-carrying wire is given by Equation 1 below;

B= (μ0i)/(2πr)

where i is the current and r is the distance from the wire. The magnitude of the force exerted on a current-carrying wire by a magnetic field is given by Equation 2 below;

F =iLBsinθ

where i is the current through the wire, L is the length of the wire, B is the magnitude of the magnetic field and θ is the angle between the wire and magnetic field.

-The length of the top and bottom wires of the apparatus with markings every 1 mm with its length found to be closest to the point half way between the 278 mm and 279 mm markings.

-The length of the bottom wire was measured with markings every 1mm and its length was found to be closest to the 288 mm marking.

-A small mass placed on the top wire weighed 5.0 g.

-The distance (center-to-center) between the top and bottom wires in the baseline position was measured to be 0.500 ± 0.005 cm.  For this experiment, the student was required to complete the following steps:

-Measure and record the length of the top and bottom wires of your apparatus.

-Setup the apparatus so that the top wire is balanced close to (but not touching) the bottom wire. Connect the apparatus to the power supply so that current will run through the top and bottom wires in opposite directions. Now turn on your laser and point it at the mirror on top of your apparatus so that it reflects toward the wall. Mark the position of the laser beam on the wall, this will be your baseline position.

-Carefully measure the distance between the centers of the top and bottom wires making sure not to bump the apparatus. Check that the laser beam has not moved from its baseline position. -Now place a small (5 g) mass on the top wire. This will add a force to the top wire that brings it closer to the bottom wire. You should see the laser beam move below its baseline position. -Turn on the power supply and begin increasing the voltage. As you increase the power supply voltage, a current will run through the apparatus and you will see the laser beam start to raise. Increase the voltage of the power supply until the laser beam is back to its baseline position. If you “overshoot”, decrease the power supply voltage and try again.

-Record the current that runs through the apparatus.

-Turn off your power supply, remove the mass and repeat this measurement 10 times. When the mass is placed on the top wire, its weight pushes down on the wire and brings it closer to the bottom wire. When the current is run through the apparatus, the magnetic field exerts a force on the top wire that counters the weight of the mass. By adjusting the current, the magnitude of the magnetic force is also changing. When the laser beam returns to the baseline position, the force exerted on the top wire by the magnetic field exactly cancels the force exerted on it by the mass. The collected measurements are as follows;

7.81 A

7.72 A

7.90 A

7.85 A

7.81 A

7.77 A

7.79 A

7.82 A

7.83 A

7.80 A

B. Please show your work to solve for μ0 in Equation 1.

C. What is the percent error. Please show your work.

D. Does your measured value for μ0 agree with the expected value? (Hint: Calculate z to solve) Please show your work.

E We have ignored Earth’s magnetic field in this experiment. The magnitude of Earth’s magnetic field is approximately 55 μT. Could this field have a significant affect on our experiment? Please explain. (Hint: Compare the magnitude of the magnetic field that exerted a force on the top wire to the Earth’s field.)

F. What is the effective resistance of the apparatus?

I NEED HELP WITH B-F.

Data listed in the paragraph above(278,288,5.0g) average A is 7.81.

Answer #1

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