Physics - Electricity

The Difference Between Volts, Amps, and Watts Explained Simply

All three describe electricity, but each measures something different. The easiest way to picture it is as water in a hose.

The water analogy

Volts (voltage, U): the water pressure in the hose - how hard is the current "pushing"?

Amps (current, I): the amount of water actually flowing - how much current gets through?

Watts (power, P): how much "work" the water can do overall - pressure and amount combined.

P = U · I Power (watts) = voltage (volts) · current (amps)

đź’¬ Mia asks Grandpa Theo

Mia

Why is a 230-volt wall outlet more dangerous than a 9-volt battery, if both are "just" electricity?

Grandpa Theo

Because higher voltage (volts) has more "pressure" to push current through your body. More pressure means more amps flow through you - and it's the amps that harm the body.

Mia

So what does "60 watts" mean for a lightbulb?

Grandpa Theo

That's the power - how much energy is used per second. At 230 volts, a bulb like that only needs about 0.26 amps: 230 · 0.26 ≈ 60 watts.

Example

A device runs on 230 volts and draws 2 amps. How many watts is that?

P = 230 · 2 = 460 watts

In Europe, mains voltage from the wall outlet is 230 volts. In the US it's only about 120 volts - which is why American devices need roughly twice as many amps for the same power.

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