CURRENT ISSUE
Contests
Test your eq
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Issue #234 January 2010
Problem 1—Whatever happened to “Bubble Memory”? It seems to have disappeared without a trace.
Problem 2—What’s the difference between an Ethernet hub and an Ethernet switch, and what are the key tradeoffs?
Problem 3—How exactly does a multi-master I2C bus work?
Problem 4—An alkaline AA cell has a nominal operating voltage of 1.5 V and a capacity of about 2000 mA-h. It weighs about 23 grams. By how much does its weight (mass) change between being fully charged and fully discharged?
a. Not at all
b. 0.12 nanogram
c. 41 micrograms
d. Other
For reference, the electron charge-to-mass ratio is about 1.76 × 1,011 C/kg, and the speed of light is about 3 × 108 m/s.
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