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How does a 'voltage drop' work?

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It is my understanding that, in an electric circuit, voltage is divided amongst components in a ratio determined by their various resistances. That is, for example, if a 5Ω‎ and a10Ω‎ resistor were placed in series across a 12V power supply (assuming negligible resistance in wires), then the voltages across the 5Ω‎ and 10Ω resistors‎ would be 4V and 8V respectively – that being the EMF of 12V being divided in the ratio 2:1 as defined by the resistance values, correct?

However, some components aren’t like this, and I’m interested to know why. Take for example the base of a transistor. The base is said to ‘drop’ around 0.7V between itself and the emitter, rather than being described as having a resistance value. It’s easy enough to work with just by using a voltage divider, but it still seems a weird concept and I would very much like to know how this works.

Thanks in advance.


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