Dr. Schmidt explains the world: unplug more often

Steffen, I noticed that when I unplug the charger for my phone from the socket, it continues to hum for a while. Is something broken?

These chargers have capacitors in them and they discharge when you unplug them. This can cause vibrations that you then hear. As long as the part doesn’t get hot, everything is okay.

A charging cable is something other than just an extension cable…

Completely decided along with the charger. This has to turn 220 volts alternating current into 12 volts direct current.

Now you shouldn’t leave things in the socket to save electricity. I thought electricity needed a circuit to flow.

A circuit is also available. There is a transformer in the charger, i.e. a coil that converts voltages. A current always flows through the input coil. Old Tesla came up with the principle: If you build a coil with many turns around a coil with a few turns, then the ratio of the turns of the coil is the same as that of the input voltage to the output voltage. However, without a load behind it, only a small amount of current flows.

As much as electrical appliances in standby mode?

Not quite, there are functions that are actually permanently supplied with power. For example, there are people who, like me, record certain television shows. This requires that the control electronics that ensure that the device knows what time it is and when it should record is supplied with power. Then the consumption is a little higher because something is actually happening.

But such multiple sockets with switches are just extension cables where you don’t have to pull everything out of the socket individually?

Some also offer protection against surges. But it is practical. If a PC and monitor are connected to a power strip like this, perhaps an external speaker…

… you can turn everything off at once.

That makes perfect sense. Although standby mode on computers is now more economical than before. I read somewhere that it now saves a lot more energy on televisions and monitors if you set them a little less bright than if you completely unplug them from the mains.

But I once heard that laptop power supplies can get hot if they are left plugged in for too long.

Nope. If the things aren’t defective, nothing will happen. However, if you constantly have the power supply connected to the notebook, it also depends on the notebook battery being OK. In general it’s not that good either because the battery then discharges a little and then charges again, and the lifespan of modern lithium batteries depends on the number of charging processes.

So only connect it when the battery is empty?

Not that either. The batteries also suffer from deep discharges. Many cell phone manufacturers have a control system that only charges the battery to 85 percent. But you have to find this attitude first. Not everyone has it, and most of the time it’s well buried.