Exam 2 practice problems - Exam #2 practice problems 1. So...

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Exam #2 practice problems Physics 227 1. So far in the course we have not been able to design an experiment that could decide if the moving charged particles that make up currents in wires were positive or negative. We’ve been using the convention that they are positive and we’ve defined electric current to be in the direction of motion of these positive charges. However, we also know that it could be that it is actually negatively charged particles traveling in the opposite direction . Suddenly, you have an idea! A straight wire carrying a current is placed between the poles of a strong horseshoe magnet as shown. You realize that if you take a voltmeter and touch its two terminals to opposite sides of the wire (see the side view) you can actually answer the question of what the sign of the moving charges are. Explain in detail what is happening in this situation and why it can be used to finally answer the question. Hint: If the moving charges are positive, what will be happening to them? If they are negative, what will be happening to them? 2. Consider the circuit below. You can consider the wires and battery as ideal, having negligible resistance. Predict what the currents through each of the resistors will be. 3 R 2 R 1 R 1 2 1 2 1 2 3 3.00 7.00 6.00 4.00 2.00 V V R R R  3. Two long straight wires are carrying currents as shown in the diagram. The wires are in contact but are insulated from each other. The wires are free to move with respect to each other (slide, twist, rotate, curl up, do nothing, etc.). Initially there are no currents flowing in the wires. Predict what will happen when the currents are turned on and justify your prediction in detail. S N I S N Side view
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4. Two long straight wires carrying currents of 3.00 A are aligned as shown. Predict the magnetic field generated by these wires at the point     , , 0.2 ,0.2 ,0.2 P x y z m m m . 5. A hydroelectric power plant generates 5 megawatts of power. This is transmitted to a city 30.0 km away through 2 power lines (since it needs to be a closed circuit) made of copper wire (resistivity 8 1.72 10 m  , diameter 4.115 mm ). If the power lines carry a current of 70.0 A what percentage of the power generated by the power plant will be lost in the wires? 6. In the particle beam in the previous problem there will be a large number of protons traveling in the same direction in close proximity to one another. Understanding how the protons interact with each other is crucial to understanding the behavior of the beam. One way to start analyzing the situation is to consider how just two protons traveling parallel to one another will interact. So, let’s say there are two protons side-by-side separated by 10 1 10 m traveling in the +x direction at 1.00% of the speed of light.
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Exam 2 practice problems - Exam #2 practice problems 1. So...

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