# Powering a circuit: electricity

## Powering a circuit: electricity

Tame electrical waves and currents.

### 7. Ohm's law

Let's imagine the ball again. If you have a small ball travelling at a very high speed, it could potentially have as much or more power as a large ball travelling at a very low speed. In this way, you could say there is a direct relationship between the speed a ball is travelling, the size of the ball, and the potential power of the ball.

Of course though, we are actually not really talking about balls, but
electricity. When dealing with electricity, voltage and current are in a
direct relationship with power. In a circuit, power is expressed in
terms of Watts. The symbol for this is a **W**.

Watts = Voltage * Current

There is also another factor we have yet to talk about that also plays a
role, and that is **resistance**. In our analogy, resistance is the
headwind that the ball must fight against to move forwards. On a calm
day, there might be little resistance to its flight, but on a windy day,
it might have to fight against the wind pretty hard. Again, we are
actually talking about electrical resistance in a circuit and not
throwing a ball.

Resistance pushes against the flow of electricity. As such, it is also in direct relationship with Watts, Voltage and Current. Resistance is expressed in Ohms (after it's discoverer). This mathematical relationship between Watts, Voltage, Current and Resistance is unsurprisingly called Ohm's Law.

Ohm's Law is not something you must memorize, but it will play an
important role later when determining how much resistance a circuit __must__
have. Thanks to this law, a circuit having a minimum amount of
resistance is not optional, but necessary. The energy in the circuit
must encounter resistance in order to expend itself. The thing in the
circuit which uses energy is considered the Load. If an electrical
supply is connected to ground without a load to use up the energy, bad
things will happen.

##### You should **NEVER**
connect your positive voltage source directly to ground.

**NEVER**

One of the other fundamental concepts of
Ohm's Law is that electricity must encounter a minimum amount of
resistance in a circuit and be able to expend itself. If you connect
power and ground directly together, there will be a lot of energy that
has no way of expending itself. Your circuit will then try to release
this unused energy in highly antisocial ways. Basically, the energy will
turn into heat. However, having nothing in particular to warm, either
your power source or wire will start to dramatically heat up. This can
potentially result in a damaged power supply, melted wire, a fire, or
potentially an explosion.

Another name of this phenomena is a "short circuit." You likely have heard this term before.