Part A: When the power supply is switched on, what is the current? Answer I= ___

Question

Part A: When the power supply is switched on, what is the current? Answer I= ____ Value _____ Units?

Part B: What is the magnitude of the force on the wire? Answer F= ____ Value _____ Units?

Part C: What will be the wire's speed after it has slid a distance of 7.4cm? v= ____ Value _____ Units?

A device called a railgun uses the magnetic force on currents to launch projectiles at very high speeds. An idealized model of a railgun is illustrated in the figure. A 1.2 V power supply is connected to two conducting rails. A segment of copper wire, in a region of uniform magnetic field, slides freely on the rails. The wire has a 0.71 m ohm resistance and a mass of 5.0g. Ignore the resistance of the rails. (Figure 1)

Explanation / Answer

1) Since you know voltage (1.2 V) and resistance (0.71 milliohms), you can find current using Ohm's Law: voltage = current * resistance. Substitute the values you know and solve for current. (Note than a milliohm is a one thousandth of an ohm.)

2) To find the force you'll need to know the strength of the "uniform magnetic field" that you mentioned. How strong is it?

3) Once you have the force on the wire, you can find its acceleration by Newton's Second Law (force = mass * acceleration). Then set up a differential equation and use calculus to find the velocity when position = 6cm.

With this in mind

I = V/R = 1.2/0.71x10-

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