If someone bought an electrical appliance in the US would it work in the UK given US appliances use 120V and UK use 240V?

I was a US Government employee. Me and my family were sent to England where we resided for 7 years. We shipped all our household goods with us including all our US electrical appliances. Once there, we purchased transformers which come in various wattage ratings. The transformer actually converts the 220voltage down to the required 120 volts for US products. Anything with a motor would only be turning at 50 cycles a second vise the 60 cycles of US current. This would only affect the playing speed of say a record player (obselete now) but radios, toasters, coffee pots or anything of that nature would work fine. Hope this has helped.

You need a transformer, as mentioned above.

Note that for running UK appliances in the US that is not necissarily true, as the US has 120/240V service. You'd just need a special outlet for your 240V appliances.

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Some, but by no means all, electronic appliances have 110/240V switches to allow use on either system.