Why is it bad to put metal or magnets near your phone, tv etc?

[nst.john]

I've had my phone messed up before by metal and I wondered what the metal did to my phone, I'm guessing it maybe grounded the battery but I'm not sure. Can someone explain what happens when a metal or magnet interacts with electronics? And also is there any way to fix this if that did happen to one of your devices?

 

[DrZoidberg]

Could you be more specific? If some metal object gets into the battery compartment it may short out the battery. That can cause it to become very hot and could destroy the battery. In case of a lithium battery it can also cause a fire. Metal touching the outside of a device should not do anything except of course if it hits your device very quickly. Magnets will in most cases not cause any problems but there are a few exceptions e.g. old crt tvs don't like magnets. They are also not good for credit cards or hard disks.

 

[Averagesupernova]

Had a close lightning strike about a month ago and I have a tube-type TV that was on at the time of the strike. The shadow mask inside the tub was severely magnetized from this strike. I have never seen one get that bad. I have used magnets to mess up the tubes in TVs in the past and never was able to get one to look quite that bad. A power cycle of the set took care of it by running the internal degaussing coil. Typically magnets don't permanently damage anything except a type of magnetic memory storage.

 

[Baluncore]

The shadow mask in a colour TV is degaussed at switch on to cancel the local orientation of the Earth's magnetic field.
Experimenting with strong magnets near the screen can physically distort the shadow mask sufficiently to make a permanent change to the phosphor dot alignment with the mask. That physical damage cannot be degaussed, it is permanent.

A magnet can also be a problem near any inductive component such as a transformer. A strong magnetic field can bias the core material and so result in asymmetric saturation that will generate even harmonics in the signal. That principle is applied in the flux gate magnetometer.

Power supplies often transfer energy through a magnetic coupling. If the magnetic core is biassed then the capacity of the power supply can be significantly reduced.

The presence of a metal conductor near a mobile phone can absorb significant power. It can also reflect the signal with a path length and phase that may result in destructive interference in the direction needed for communication.

 

[Averagesupernova]

The shadow mask in a colour TV is degaussed at switch on to cancel the local orientation of the Earth's magnetic field.
Experimenting with strong magnets near the screen can physically distort the shadow mask sufficiently to make a permanent change to the phosphor dot alignment with the mask. That physical damage cannot be degaussed, it is permanent.

Yes if we PHYSICALLY move the shadow mask that will be a problem. Same thing can happen from a dropped TV or monitor.