QUES: The current–voltage characteristic of an LED is similar to other diodes, in that the current is dependent exponentially on the voltage (see Shockley diode equation). This means that a small change in voltage can cause a large change in current. If the applied voltage exceeds the LED's forward voltage drop by a small amount, the current rating may be exceeded by a large amount, potentially damaging or destroying the LED. The typical solution is to use constant-current power supplies to keep the current below the LED's maximum current rating. Since most common power sources (batteries, mains) are constant-voltage sources, most LED fixtures must include a power converter, at least a current-limiting resistor. However, the high resistance of three-volt coin cells combined with the high differential resistance of nitride-based LEDs makes it possible to power such an LED from such a coin cell without an external resistor.

How are non-LEDs similar to other diodes?
What is the answer?
ANS: unanswerable
QUES: The government has established an Integration Office under the Department of Foreign Affairs and the Department of Economic Affairs. To minimise the negative consequences of Switzerland's isolation from the rest of Europe, Bern and Brussels signed seven bilateral agreements to further liberalise trade ties. These agreements were signed in 1999 and took effect in 2001. This first series of bilateral agreements included the free movement of persons. A second series covering nine areas was signed in 2004 and has since been ratified, which includes the Schengen Treaty and the Dublin Convention besides others. They continue to discuss further areas for cooperation.

When was a second series of 9 bilateral agreements signed?
What is the answer?
ANS: 2004
QUES: The density of paper ranges from 250 kg/m3 (16 lb/cu ft) for tissue paper to 1,500 kg/m3 (94 lb/cu ft) for some speciality paper. Printing paper is about 800 kg/m3 (50 lb/cu ft).

What is the range of paper dryness?
What is the answer?
ANS:
unanswerable