I keep a thin paper booklet with a magnetically encoded stripe in the same thin protective case as my 2020 MacBook Air, and when it’s in my backpack it’s pressed to the bottom side of the laptop.
Three times now I’ve had to have the stripe rewritten or replaced, and it suddenly occurred to me that it may be related to the laptop.
The laptop power is off (laptop shut down thought the battery still discharges slowly but the fan isn’t running to my knowledge.
Question: Does my 2020 MacBook Air have an external magnetic field that might be erasing a magnetic stripe pressed against the bottom? If so, where is it? Back, left/right side, front, middle?
I first thought of MagSafe, but of course this model doesn’t have it.
“bonus points” This is pure physics curiosity; if there is a magnetic field, does Apple have a spec for how strong it is? Earth’s field is of order a half gauss, I’m just curious how strong it might be.