To rectify batter voltage\n\nTo regulate battery power\n\nTo prevent reverse charging of the batteries\n\nto provide a reverse friction at the switch
200933
No wonder all the engineering jobs go over seas. Nobody here wants to learn.
383788
You need to specify how much current is going to be drawn from the battery, and also, how long you expect the circuit to operate before the battery needs to be replaced.  If you don't know, describe exactly what the application is, and maybe I can come up with a good estimate.  Note: it's usually a lot better to use a voltage regulator than just a pot.
55765
To answer your question first: Yes, it will generate a back EMF in the circuit each time the power to the electromagnet is turned off, but this energy is never equal to the energy which was originally applied when you turned the switch on.  Nothing in life is free :)  \n\nWhat you're describing is actually called a transformer. A transformer works by applying an alternating current (equivalent to turning your hypothetical switch on and off very quickly, many times per second) to one coil, which induces current in another coil (or several, depending on the design).  \n\nWhile a transformer can be relatively efficient, it can never be 100%, and certainly not MORE than 100%, as you describe.
350061
Yes, to protect respective power blocks
508455
An inverter is a circuit for converting direct current (DC) to alternating current (AC). Inverters are used in a wide range of applications, from small switched power supplies for a computer to large electric utility applications to transport bulk power.\n\n--> http://en.wikipedia.org/wiki/Inverter_%28electrical%29\n\nAn uninterruptible power supply (UPS), uninterruptible power source or sometimes called a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available.\n\n--> http://en.wikipedia.org/wiki/Uninterruptible_power_supply
609057
Hotwire around it in the circuit.  Cut the lead feeding into the filter after the jumper.\nJust like bypassing a sensor in a burglar alarm system.
156641
atach a wire to each part of the batter, attach them to the light. create a circuit and you will have light
78748
You should remove the batteries because even if they are not used, the chemicals in the battery can eat through the housing and damage the device.\n\nAlso, the chemicals in the batteries have a "shelf-life" where they will react slowly even if there is no electrical discharge.
623045
a because the voltage starts off small with little tuns but later increases because there are MORE turns and then the voltage increases...i think.
487178
Running an electric motor "backwards" generates electricity.
317350
b) and c)\n\nthe transformer works in such a way that electric current flows through the secondary circuit only when the electric current in the primary circuit is changing.\n\nwhen you close the switch the electric current in the primary circuit suddenly rises from 0amp to some value\nwhich causes electric curent to flow through the secondary circuit\n\n.. b) is true\n\nwhen you open the switch the electric curent in the primary circuit changes from the maximum value to 0amps thus electric curent flows through the secondary.\n\n.. c) is true\n\nbut \n..a) is false\n\nsicne a battery is a dc source wich means that as long as the switch is closed it supplies a steady amount of electric current through the primary. thus ther will be no current through the secondary.
557847
yes, it is a step-up circuit.\nYou can get many volts if you know what you are doing.
659911
put voltages source in parallel to charge the capacitor, and a resistor in series to discharge.\n\nofcourse , you needto use a switch to control the charging or discharging.
622604
At work we just got motion sensitive switches.  If there isn't any movement for so long, the lights turn themselves off.  Saves a bunch on electricity.  Of course they automatically turn themselves back on when we walk through.
515946
It was a safety measure to avoid electrocutions. It works even though it costs more for the wires. \nSome people think it was to match battery supplied electrical systems but that is not right.
638976
Some cars do take advantage of the car's kinetic energy while braking in order to recharge batteries or do some other form of work.  It is often used in hybrid type cars which are designed to get such great city driving gas mileage (but have pretty average highway driving mileage) since the car tries to conserve as much of the energy of possible when stopping.\n\nBy converting the car's kinetic energy into some other form of energy (be it chemical potential, or what-have-you), that energy can be stored for later use.\nRemember, no energy conversion is/will ever be 100% efficient, there will always be some loss.\n\nIt is not always possible/practical do implement this type of feature in every situation.  For example, if you have to slam on your breaks and stop the car ASAP, you dont have time to wait for a generator to charge up a battery, it would be "better" to just "Waste" the energy and transfer it into heat.
109081
First of all the physical care. Find an protective carry case, keep it from heat & cold & Water.\nIt is a good idea to let the battery run down the first few times and then recharge. I am told this is good for prolonging the life of the battery.