Quote:
Originally Posted by jyl
E = I R
Suppose R x100 means E x100 and I unchanged
W = E I
So W x100
Thus by merely raising the resistance, you can get arbitrarily more voltage E and power W from the source. With sufficiently high resistance, I can get millions of volts and millions of watts from a AAA battery.
Very cool, if it were true.
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You can get very high voltage from a low voltage source, but not that way.
You hook up a battery to an inductor. The current becomes stable and it creates a magnetic field. If you suddenly open the circuit, the magnetic field breaks down which creates a voltage across the switch. This energy in the coil needs to go someplace. The voltage will increase until it "jumps" the gap. And that is usually a big spark. This is why there are little resistors in parallel with most coils, to bleed down the energy in the coil.
Kids used to make surprise sparkers with a box (usually an old cigar box, something with a hinge) some insulated wire, a battery, a good sized nail or bolt, some aluminum foil and some tape.
You wind the wire around the nail, which makes the inductor, then use a little tape to keep it in place. Tape the battery to the bottom of the box. Cut a couple of pieces of narrow strips of foil. Tape one piece to the box top and the other to the box side, lined up to create the switch. Now tape one end of the coil wire to the foil on the side and the other coil wire to one end of the battery. Finally connect the foil on the top side to a spare piece of wire and then connect and tape that wire to the other end of the battery.
Close the box and hand it to someone. When the open the box, a big spark will cross the foil contacts. Hilarious!
