Is 240V AC or DC UK?

UK mains is 230 or 240v ac 50Hz . 50Hz means that the voltage cycles 50 times per second. For UK mains, the peak voltage is around 330v, and the overall ac waveform gives the same heating effect as 240v dc would. It is called 240v because it is equivalent to 240v dc for heating and lighting.

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Why does America use 110V 60Hz?

North America and Japan use 110V/60Hz electricity where as rest of the world use 220V/50Hz. The reason was historical. Engineers in USA originally laid lines for 110 V where as in Europe they did with 220 V. After that, it would have been too expensive to change the system .

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