084 – Current, Voltage, Resistance
All electrical circuits function by controlling the flow of electrons.
Written by Scott Adamson
Whenever we’re on stage as technicians or musicians, we’re handling electricity in some way. It’s critical that we understand how to safely manage electronic equipment used to power shows, though certain tasks must be left to qualified electricians.
Let’s talk about three principal concepts of electricity: current, voltage, and resistance.
Electrons are the negatively-charged subatomic particles at the root of electricity. A circuit is the signal path in which electrons flow. Current describes the flow of electrons — specifically, the amount of electrons flowing per second. For this to happen, a circuit must be a closed path, meaning that current can flow along the entirety. A break anywhere in the circuit will stop the flow. Current is measured in a unit called amperes, named after the French mathematician and physicist, André-Marie Ampère, but we often abbreviate that to amps.
Voltage is the electrical charge, or potential energy, between two points, where one point has a higher voltage than the other. Think about a 9V battery. The potential charge between the positive and negative is 9V. The unit we use to measure voltage is the volt, named after Italian physicist Alessandro Volta who is credited with inventing the first electric battery in 1800. A device called a voltmeter allows us to measure the voltage in a circuit.
When current is multiplied by voltage, we get Watts, an important unit of power.
Resistance restricts the flow of electrons. It’s a measure of the opposition to current flow, measured in Ohms, named after German physicist Georg Simon Ohm, and symbolized by the Greek letter Omega (Ω). In electronic circuits, passive electronic components called resistors are used to create varying degrees of resistance and reduce current flow.
All materials resist current flow to some extent, but we break them down into two distinct categories: conductors and insulators. Conductors are materials that have very little resistance, allowing electrons to move easily. Copper is a common conductor used in a lot of audio equipment. Insulators, on the other hand, have high resistance which restricts the flow of electrons. Two examples are glass and wood.
Let’s think about an analogy. Electrons flow similarly to water.
Imagine we have a water tank with a hose. If the water is flowing through the hose at a rate of one gallon per second, this measurement would be the current, the rate at which charge flows. It’s a measure of the number of electrons flowing per second.
Just like current is similar to the rate of water flow, voltage is similar to the water pressure. Again, in electrical terms, voltage is a measurement of the difference in electrical charge between two points. The tank has more water, or charge, than the end of the hose, which creates pressure. We can think of the water tank as a battery, which would eventually run out, or a continual power source like the electrical grid. These sources hold tons of electrons that are available to flow through our system. However, if there was a tank on the other side with an equal amount of water, the pressure would be equal and nothing would flow through the hose. If one side is totally open with no resistance, the pressure is going to make the water flow through the hose. In an electrical circuit, it’s this pressure that we measure in Volts. This is the potential energy between two points.
Get real-world live sound mixing tips straight to your inbox.
In our water system, we see resistance as a valve that can allow more or less current to flow. If we tighten the valve, we add more resistance and less water can pass.
The final output of the system represents Wattage, or the total power.
All of these principles of electricity are related. If one changes, the others will also change. We can define this relationship in an important equation — Ohm’s Law.
We’ll cover that next week. Stay tuned!
