What are the different means by which these devices get energy?

Question

which device is used to operate a radio when there is no current?

what is used to get electric power in cars and buses?

what is used to get electric power in watches and calculators?

what is used for operating mobile phone , emergency light etc.?

AND ALSO TELL

which of them can be reused and also those which are disposed of after use.

Answer 1

batteries

watches and calculators i would think are the only ones that need to be "disposed after use" provided they use those small batteries.

Answer 2

- Crystal radios use the vibrations in a quartz crystal and an electric coil to receive radio signals without needing to supply power:  http://en.wikipedia.org/wiki/Crystal_rad...  They are powered by the electricity sent through the signal (about 91%, only 9% carries the signal itself).

- Hybrid Cars  and electric cars can coast downward, Hybrids use gasoline engines to keep the battery charged and switch off when not being used or charging the battery.  Newer ones use regenerative braking (http://en.wikipedia.org/wiki/Regenerativ... this takes some of the forward moving energy and uses it to spin a rotor so that it will be resisted causing both braking and power generation.

- Calculators often use small watch batteries for power supplemented with a solar cell (http://en.wikipedia.org/wiki/Solar_cell) to keep the power drain low.

-  Emergency phones and lights set up on the road or by trails are sometimes tied into the power grid, but more often are powered by lead acid batteries (http://en.wikipedia.org/wiki/Lead-acid_b... that are charged by solar cells.  Hand held ones are almost always powered with rechargeable batteries.  One problem with the Apple iPhone is that replacing the battery violates the warranty and requires taking the phone apart.

Solar cells are renewable energy sources, with no moving parts and can last 20 years or more.  Batteries have a limited lifespan before the chemical reaction is depleted and they are drained.  You can extend the life of batteries by inputting energy and rechargeable batteries are designed to do this, but even they have limited lifespans.

Disposal of batteries is dangerous because many of them use mercury a well known environment poison.  Lead acid batteries use battery acid, which can be dangerous and are most often used for emergency roadside systems and in cars.  Lithium batteries (http://en.wikipedia.org/wiki/Lithium_bat... are the new technology powering both laptop computers and electric cars.

The battery in a watch is probably a lithium one.  Most standard batteries are alkaline batteries (http://en.wikipedia.org/wiki/Alkaline_ba...  Lithium batteries use a wide range of chemicals and so some of their contents can be dangerous, but on average they are safer and last longer than alkaline or normal batteries.

Crystal radios receive AM signals which cannot carry stereo signals so they are almost never used anymore however hobbiest still make them and Radio Shack sells do- it-yourself electronic kits that contain them.  Quartz, in a crystal radio, is not a problem nor is the copper and most of the other components, which can be easily recycled.  Otherwise the technology is antiquated and seldom used.  Broadcast power (first proposed by N. Tesla) is making a comeback and uses similar technology to recharge cell phones or to power small devices without wires.

ALL things eventually wear out and need to be disposed of, but the primary ingredient of solar cells is silicon; the primary ingredient of glass and sand.  The rare metals in them can be recovered and the silicon can be reused.  Batteries though are problems and disposing of them in landfills is a major problem (Battery Recycling:  http://en.wikipedia.org/wiki/Battery_rec...

Answer 3

There is no radio that can operate without current. Even a crystal radio, which uses no battery or other apparent source of electrical power or current, uses the current received from radio waves by way of an antenna and ground connection.

Electric power in cars and buses comes from a combination of batteries and an alternator driven by the engine.

Electric power in watches and calculators comes from batteries or photovoltaic cells or a combination of the two.

Mobile phones and emergency lights usually use batteries. Emergency lights may use AC power to keep internal batteries charged, which they rely on for use.

Any of these items can be disposed of after use. The ones that use batteries can be reused by putting fresh batteries in them. You may have to dispose any batteries when they're exhausted, but not as often if they use rechargeables.

Answer 4

1) "operate a radio when there is no current" is a meaningless statement. You can't operate a radio without some sort of power/current. If you mean a battery, then there IS current.

2) Cars get electric power from an alternator and battery

3) watches and calculators get power from batteries

4) also from batteries

radios, cars, busses, watches, calculators, mobil phones can all be reused. None are disposed after use, unless you are really careless.

I realize English is not your first language, but you need to work on the grammar!

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