## Friday, November 5, 1999

### What is the the relation between volts, amperes and kilo-watt hours?

What is the the relation between volts, amperes and kilo-watt hours? Also,

where does BTU fit in?
Well a volt is a measure of potential difference. What this means is that it is a measure of the difference in electric "levels". You can compare it to a waterfall. Water will fall over the waterfall only if the water at one end is higher than the other. So we can say the measure of "potential difference" between the top of the waterfall and the bottom is the height of the waterfall. Similarly, electricity will flow only from a point that has a higher potential to apoint that has a loweer potential - that is a positive potential difference.

An ampere is a measure of the amount of electricity flowing. For example, if we have the Niagara falls, it will have a large amount of water flowing over it (or a greater number of "amperes") than a smaller waterfall in Khandala.

Here we have to introduce a new concept - resistance. Resistance is measured in ohms, and is the resistance to the flow of electricity. Resistance being same, a larger voltage (potential difference) will result in a higher current (amperes). But, if you increase the resistance, the flow of current (amperes) will reduce. What I have just explained is known as Ohm's Law, and is mathematically stated as current is directly proportional to the voltage, and the proportionality factor is the resistance, or:

V = iR (V = voltage, i = amperage, R = resistance)

Next we come to the concept of power. Power is the amount used per second. Electric power depends on the voltage (the potential difference). To increase the voltage requires energy. Power also depends on the current - the greater the current, the greater the electric power. So we arrive at a simple mathematical form:

P = Vi (P = power, V = voltage, i = amperage)

Power is measured in watts, and a 1000 watts are a kilowatt. As I mentioned earlier, power is the energy consumed per second. If you want to know exactly how much energy has been consumed, you need to know how much time that you have been using the power. This is commonly measured in hours. So, the measure of total electric energy consumed is measured in kilowatt-hours.

Energy = PT (P = power, T = time)

OR

Energy = ViT (V = voltage, i = amperage, T = time)

A BTU is an imperial measure of energy.