# Voltage and Current

1. Nov 11, 2008

### kiamzattu

Hi every1
Can somebody tell me how is high voltage produced with low current? I mean Current and voltage are directly proportional. So if there is high voltage then there must be high current right? Ok it also depends on the external load connected (R). But is there any way of having a high voltage source and still reduce its output current? does it has anything to do with internal resistance of the source. I mean if there is a high voltage source with a high internal resistance then its output current is low. so is it a high voltage low current source?????

also can somebody also explain about low voltage and high current source?

Any help would be greatly appreciated.

2. Nov 11, 2008

### rbj

sounds like you figured this out yourself. think of Thevinin and Norton equivalents. high voltage in series with high resistance is the same as a not-so-high current in parallel with the same high resistance. this is why these electric fence controllers that farmers/ranchers use to control livestock have enough kick (whether the ground is wet or dry) to keep the cattle at bay, yet the rancher's 8 year-old kid doesn't die of electrocution if he/she were to happen upon the electric fence. the current is limited even if the "load" as 0 ohms.

car battery. arc welder.

3. Nov 11, 2008

### Proton Soup

you can have high voltage high current, and low voltage low current. it's just a question of power.

4. Nov 11, 2008

### kiamzattu

Thank u for ur replies.

Since its a question of just power i've studied that X-rays and electron microscopes require high voltage(DC) and not so high current. So if we are to power X-rays with a high current and not so high voltage will they Work? (Assuming both the cases produce the same amount of power).

5. Nov 11, 2008

### Proton Soup

no, some processes are going to require high voltage, and some are going to require lower voltage. the more power you need, the more current you'll need. a 1000 watt x-ray generator should require twice as much current as a 500 watt x-ray generator. if you wanted to produce a gigawatt, then you'd need a whole bunch of current for the same voltage. it all depends on the application.

6. Nov 15, 2008

### kiamzattu

Thank u guys for ur replies.