A plastic hose stuffed more or less densely with steel wool and a source of water can act as a model for resistance and electric current in wires. Suppose two one-meter lengths of such a hose were stuffed identically with steel wool
Discuss how one could use this model to determine which of the following would have greater resistance: one length; two lengths connected one after another; two lengths connected side by side, both connected to one source of water. Speculate on the answers as best you are able.
This exploits the model discussed above for resistance. The single lengths of hose
have the same resistivity—caused by the steel wool stuffing. Connect two hoses in series
(one after another) and the resistance increases. Connect two hoses side by side (assume
that it is possible to do so without leaks occurring), and the water has more ways to get
through to the other side—there is less resistance. Two lengths side by side has the least
resistance of the choices offered; two one after the other has the most resistance. In fact, by
our argument, the two side by side have half the resistance of the single length, and the two
one after another have twice the resistance of the single length.
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You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor. If you want to achieve the largest possible resistance, you should attach the leads to the opposite faces that measure
A) 3 cm × 5 cm. B) 3 cm × 8 cm. C) 5 cm × 8 cm. D) Any pair of faces produces the same resistance.
The wavelength of the red-pink line emitted by a laboratory sample of excited hydrogen is 656 nm. Taking a spectrum of a glowing nebula, you find that the same red-pink line of hydrogen appears at 662 nm. You conclude that the nebula
A. is moving away from us at about 1% the speed of light. B. is 1% hotter than hydrogen in the laboratory sample. C. is moving toward us at about 1% the speed of light. D. is 1% cooler than hydrogen in the laboratory sample.
In a single-slit diffraction experiment, the central maximum is broadened if the wavelength of light increased
Indicate whether the statement is true or false