On Java Edition, try the interactive map designed to accompany the tutorials.
OK, fair warning. This chapter might be a bit of a slog.
We're going to cover the concept of charged blocks, and… well, it's not glamorous. It's a little weird. Confusing. A tangle of unintuitive rules. So you might be tempted to skip.
Seriously confusing until you understand charged blocks.
Don't! Having a poor understanding of how charged blocks transmit power is probably the biggest source of confusion when learning redstone. If you don't know how this works, you'll be confused constantly. Your designs will break and you'll have a heck of a time figuring out why.
Not only will learning these rules make you more confident with your redstone skills, but your devices will be much more compact. That means less frustration trying to fit things into small builds. And it'll be much easier to hide your wiring, so you don't have unsightly cords poking out of your walls and floors!
Let's dive in.
What is a block?
First we'll clarify something that might be confusing if you haven't dabbled in the technical side of Minecraft before.
The word block can refer to at least four different things:
An area of space: "That is an empty block."
A unit of distance: "This structure is 10 blocks high."
A cube-shaped item: "I crafted a block of iron out of 9 iron ingots."
A placed object which consumes a cubic area of space: "There's a lever block placed on the stone block."
Note that placed blocks need not be cube-shaped. Levers, ladders, and lanterns are all examples of "blocks" in the sense that they can be placed into the Minecraft world grid, consuming one block of space. (In contrast, something like a sword is not a block, because you can't place it -- only drop it.)
This doesn't tend to get very confusing in practice. The most important idea here is the idea of a "block" as a (possibly non-cube-shaped) placeable object; as long as you keep that in mind, you should be fine.
One non-block item next to two blocks
Using Charged Blocks to Transmit Power
A charged block is a block which transmits power in all directions. You can think of it as a block (often something like wood or stone) that's functioning as a piece of short, weird-looking redstone wire.
A lever using a charged block and redstone wire to transmit power
Various ways of charging a block. In the rightmost configuration, the lever itself is a charged block.
There are four ways a block may become charged:
The block is powered by redstone wire (routed into its base or across its top; both are illustrated in this example).
An adjacent repeater or comparator is transmitting power into the block.
The block is charged by an adjacent active power source (for example, an attached lever is turned on).
The block is itself an active power source (again, like a lever in the "on" position).
Many power sources (including levers), when active, both are charged blocks and charge the block they are attached to. However, exact rules for how power sources charge blocks vary from power source to power source. Details will be discussed in the next few chapters.
Note that while charged blocks power other blocks, they don't charge other blocks. In other words, you can't create a "wire" out of a line of charged blocks.
The lever charges the first block, but not the second.
As mentioned above, charged blocks transmit power in all directions! This fact can be powerfully leveraged to make more compact builds, and it can also be very confusing if you don't know what's going on.
For example, when we attach a lever to a block and turn it on, we have two charged blocks -- the lever itself, and the block it's attached to. Both of these blocks transmit power in all directions, including above and below.
Two charged blocks transmitting power in all directions
Charged blocks can transmit power to redstone wire, too:
Two charged blocks transmitting power to adjacent wires
This principle can result in some unintuitive configurations. In these next few examples, the charged blocks are transmitting power to wires above and below them. (The bottom wires are technically adjacent to the charged blocks, being located one block below.)
Charged block transmitting power vertically to adjacent wires
This wire is receiving power from the lever itself (not the green block!)
The wire charges the blocks under it, which power the lamps.
When using a charged block to power a repeater, the direction of the repeater still matters. The repeater behaves as if the charged block were another piece of redstone wire.
Valid and invalid ways to power a repeater with a charged block
What blocks can be charged?
Any opaque cubic block (OCB for short) can be charged.
Examples of opaque (front row) and transparent (back row) blocks
Opaque means that light cannot pass through. Transparent (non-opaque) blocks cannot be charged. Examples of transparent blocks include glass, regular ice, and leaves.
Notably, slime blocks function as opaque blocks, even though they are visually transparent, and glowstone functions as a transparent block, even though it is visually opaque.
Cubic means shaped like a cube. Slabs, stairs, and irregular blocks like doors, chests, or rails cannot be charged.
Examples of cubic (front row) and non-cubic (back row) blocks
Examples of OCBs are dirt, wood, stone, wool, bookshelves, gravel, etc. All of these can be charged and used as power transmitters.
Broken devices trying to charge non-OCBs
Additionally, as we've seen, most power sources (levers, buttons, etc.) become charged blocks when activated, even though they are not cubic. (There are a few exceptions, which we'll cover in Chapter 5.)
In Chapter 2, we saw how routing wire into (but not across) the top of a redstone mechanism, like a lamp, only sometimes powers the lamp.
OCBs are the reason why. Wire routed this way never actually powers the lamp directly. But if (and only if) the wire is on top of an OCB, it will charge the OCB, which in turn powers the lamp.
Wiring mystery explained!
Weakly-charged vs. Strongly-charged Blocks
There are actually two types of charged blocks: weakly-charged and strongly-charged. Whether a block is weakly-charged or strongly-charged depends on how it's being charged.
If a block meets both weakly-charged and strongly-charged criteria, it becomes strongly-charged.
A weakly-charged block (dark green) and three strongly-charged blocks (light green, and rightmost lever)
The difference between these two types is that weakly-charged blocks can't transmit power to adjacent redstone wire, but strongly-charged blocks can.
Note that although weakly-powered blocks can't power wire directly, they can do so indirectly with a repeater.
Weakly-charged blocks can't transmit power to adjacent redstone wire
Terminology: POWERED, Charged, AND Activated
Before we wrap up, let's highlight some important terminology distinctions.
When a redstone component is receiving redstone power, we say it's powered. Powered lamps light up, powered doors open, and so on.
Redstone wire powering a lamp
If you don't understand the difference between charged and powered, this is really confusing.
Charged is different. Being charged means a block can transmit power, whereas being powered just means it is receiving power. Consider this example: the left lamp is powered and charged, the middle lamp is only powered, and the right lamp is neither.
A redstone component is activated when it is actively affecting the environment.
Sometimes activated is interchangeable with powered, as with a redstone lamp (it becomes activated if, and only if, it is powered). Sometimes activated is interchangeable with charged, as with a lever (it becomes charged if, and only if, it is activated). Other times it is not interchangeable with either, as some redstone components are activated only when unpowered. (We'll learn about those in the next few chapters.)
An activated/charged lever using redstone wire to power/activate a lamp
It's important to note the broader Minecraft community usually refers to charged blocks as "powered blocks" (and "soft-powered" rather than "weakly-powered").
This can get really confusing (as in the next caption), so we'll generally avoid referring to blocks as powered, instead using charged or activated where appropriate.
Terminology nightmare: A lever powers a lamp and powers the lamp's block, which in turn powers the next lamp without powering that lamp's block, so the third lamp doesn't get powered.
Chapter Summary
Charged Blocks Basics
A block can refer to any placeable item that consumes a spot in the world grid.
A charged block is a block which transmits power in all directions, including up and down.
Any opaque cubic block (OCB) can be charged.
Slabs, stairs, glass, and carpet are examples of blocks that cannot be charged.
How Blocks Become Charged
There are four ways a block may become charged:
Powered by redstone wire (routed into its base or across its top)
Powered by repeater or comparator
Charged by an adjacent active power source
Block is itself an active power source
Many power sources (including levers), when active, both are charged blocks and charge the block they are attached to. However, exact rules for how power sources charge blocks vary from power source to power source.
While charged blocks power other blocks, they don't charge other blocks.
Charged Blocks and Repeaters
When using a charged block to power a repeater, the direction of the repeater still matters.
The repeater behaves as if the charged block were another piece of redstone wire.
Weakly-charged vs. Strongly-charged
Every charged block is either weakly-charged or strongly-charged.
Blocks are weakly-charged if they are charged only by redstone wire.
The difference between strongly-charged and weakly-charged blocks is that weakly-charged blocks can't power redstone wire.
Charged vs. Powered / Activated
Charged means a block is transmitting power to other blocks.
Powered means a block is receiving redstone power from an adjacent block.
An activated redstone mechanism is one that is powered.
An activated power source is one that is generating power.
The broader Minecraft community refers to charged blocks as "powered blocks", but this gets confusing.
Next up: REDSTONE MECHANISMS!
Congratulations -- you just seriously leveled up your redstone skills! Understanding charged blocks means you can build much more compact devices, which is not only more aesthetically sharp but also allows you to create devices that would otherwise simply be impractical to integrate into tight builds.
In the next chapter, we'll take a tour of all of the redstone mechanisms. Mechanisms are what allow you to actually do things in the Minecraft world, so you’ll know how to build a lot of useful contraptions by the end of the next chapter.