1. The resistance of a superconducting material drops, essentially to zero, rather suddenly when:
(a) the sample is heated above Tc
(b) the sample is exposed to a magnetic field
(c) the sample is cooled below Tc
(d) the sample experiences a current Ic
(e) none of these. Explain your choice.
2. Imagine a length of ordinary insulated hookup wire. The wire's resistance is not dependent on:
(a) the conductor's length
(b) the conductors radius
(c) the material making up the insulator
(d) the material making up the conductor
(e) none of these. Explain your choice.
Problem
1. A particle accelerator contains two beams flowing side-by-side in opposite directions; the beams will ultimately be made to collide. One is a stream of protons (each with a charge of +1.60 x 10^-19 C), the other stream of antiprotons (each with a charge of
-1.60 x 10^-19 C). Given that either beam can deliver 1.0 x 10^14 particles per second to the colliding region, what is the net current in the machine as the two streams race past each other?
2. If the current in a 10-Ohm resistor is 500mA, what is the voltage across its terminals?
3. According to the American Wire Gauge system, No. 0000 wire, which is the heaviest, has a diameter of 11.7 mm. What would be the resistance of 100 m of copper AWG No. 0000 at 20 deg C?
4. Imagine that your are going to connect a remote speaker to your stereo system. The speaker has a resistance of 4.0 Ohm, and so you want to use hookup wire whose total resistance is small by comparison, say, 0.25 Ohm. If the speaker is to be 15 m away, what diameter copper wire should be used? [Hint: you'll need two leads.]
5. What is the maximum current that should be passed through a 100-Ohm, 10-W resistor?
6. A light bulb operating a 110 V draws 1.82 A. Determine its resistance and the amount of power it draws.
7. A credit card size calculator uses two tiny 1.5-V cells in series that provide a normal operating power of 0.000 18 W. Determine the current passing through each cell when the device is in use.