# Voltage and Wattage

1. Jan 25, 2005

### DB

1. Is it possible to increase voltage without increasing wattage?

2. If 1. is yes, then is it more common that when voltage is increased wattage increases aswell?

Thanks

2. Jan 25, 2005

### imabug

Power (in watts) = V * I

where V = voltage (volts), I = current (amps)
you should be able to figure out the answer from there

3. Jan 25, 2005

### DB

So then yes, the wattage must change (edit: with no change in amperage), thanks. But I have read (on wikipedia) that W=Joules per second or J/s ???

Last edited: Jan 25, 2005
4. Jan 25, 2005

### Cliff_J

DB - remember ohm's law as well. E (voltage) = I (current) * R (resistance)

If you have a different load that has a resistance that is proportionally higher (by a square) of the voltage change than the wattage could remain the same.

But with the same load resistance, changing the voltage will have a direct effect on the wattage.

And if you change the voltage, the current will change too.

Quick example. I have a light bulb, it has a 240 ohm resistance.

If I apply 120V to it and .5A of current flows so therefore 60W of power is dissipated.

If I apply 60V to it and .25A of current flows so therefore 15W of power is dissipated.

Now I take a light bulb with a resistance of 960 ohms.

If I apply 120V to it and .125A of current flows so therefore 15W of power is dissipated.

Notice the last two examples have the same power but with very different voltages. And typically the source of power to use electricity comes from a power supply (like the wall outlet or some form from it) or battery so its called a voltage source. To change the power, you change the resistance. Light bulbs come in many ratings of power but its really just another way to describe the actual resistance of the filament in the bulb.

Cliff

5. Jan 25, 2005

### krab

As others state, to increase voltage without increasing (wattage) requires current to decrease when voltage increases. Ordinary resistors do not have this feature, but tunnel diodes do.

6. Jan 26, 2005

### DB

Thanks guys

7. Jan 26, 2005

### Nylex

Yeah, power is defined as the rate of doing work..