Physics, 30.07.2019 02:30 kotetravels10

How much does it cost to operate a 25-w soldering iron for 8.0 hours if energy costs 8.0¢/kwh?

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The power P is defined as the energy E per unit of time t:
$P= \frac{E}{t}$
In our problem, the power is P=25 W and the total time is t=8.0h, so we can calculate the total energy used during this time:
E=Pt=(25 W)(8.0 h)=200 Wh=0.2 kWh

The energy costs 8€ per each kwh, so we can write the following proportion:
8€: 1kwh = x:0.2 kWh

where x is the price corresponding to 0.2 kWh. Solving the proportion we find x:
$x= \frac{(8€)(0.2 kWh)}{1kWh}=1.6$ €

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An electromagnet is a material in which the current produces electromagnetism and is passed to the core. so to fill in the blanks, choices would be better if there were.an electromagnet is a magnet produced by electric current with a metal core

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All these statements are related to drake's equation. it is a probabilistic equation that shows an aproximate number of civilizations in our galaxy that we can communicate with. all the numbers that are inserted into equation are not precisely known so the result varies from 1000 to 100,000,000. the equations was not created to calculate exact number of extraterrestrial civilizations but to increase scientific knowledge how to find them.the equation is: $n= r_{*} *f_{p}*n_{e}*f_{l}*f_{i}*f_{c}*l$ where: n= represents the number of civilizations in our galaxy that we could in principle communicate with today. $r_{*} =$ the average rate of star formation in our galaxy $f_{p} =$ the fraction of those stars that have planets $n_{e} =$ represents the number of planets in the galaxy that are in principle capable of having surface liquid water and life. $f_{l} =$ essentially represents the probability that life eventually arises on a habitable planet. represents the number of life-bearing planets in the galaxy. $f_{i} =$ epresents the total number of planets on which intelligent beings have evolved and developed a communicating civilization at some time in the galaxy's history. $f_{c} =$ essentially represents the probability that on a planet with life, some organisms will eventually evolve to the point where they can build radio telescopes. $l =$ is a factor that depends on how long civilizations that reach our level of technology are able to survive.

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