Flashlight Television Reaction?

Question

Recently I was dared to put a Feraday Flashlight against my TV screen. I noticed it went black in one tiny spot, and that spot didn't go away. Why is that?

Answer 1

You may be able to at least partially undo the damage you have done to your TV by magnetizing part of the screen. Some televisions degauss the screen each time the power is turned on. Do this by unplugging it, not just by turning off the switch.

Another degaussing method which MIGHT help more than it causes further damage is to use a bulk eraser for magnetic tapes, which produces a varying magnetic field. Gradually move it away from the screen with smooth circular motions.

I trust you were aware of this risk before you took the dare. And don't ever play Russian Roulette.

Answer 2

A Faraday Flashlight is one of those flashlights that you shake to provide power for the lamp. The shaking action moves a strong magnet up and down inside the flashlight. This causes magnetic inductance in a coil of wires that the magnet passes over. The inductance causes electricity to flow, thus lighting the lamp.

A regular TV shows the picture on the screen by firing electrons at the back-side of the screen. The electrons cause a phosphor coating on the glass to light up when hit by the electrons. This is what's known as a cathode ray tube (CRT).

The electrons in the CRT are affected by, and aimed with magnetic fields. The magnet in your flashlight is powerful enough to overpower the aiming magnetic fields in the CRT and disrupt the path of the electrons to the screen. This causes you to see dark spots, or different colors on the TV screen. See the link for more info on CRTs.

Note: Putting strong magnets next to TV or computer CRT's can permanently damage the magnetic coils inside, causing fuzzy or incorrect colors on the display.