| Electronics > Beginners |
| Voltage drop across resistor |
| (1/1) |
| medical-nerd:
Hiya Aaaarghhh.... I'm probably having a face palm moment but am having a blank at the moment. I know how to calculate basic voltage drops using ohm's law by calculating current flow first. But what do I do if current is a known fixed value? If I have a module that uses e.g 275mA at a supply of 5V, if there is a resistance of 10ohm after the voltage regulator, what is the voltage drop across the resistor? Cheers |
| capt bullshot:
U = I * R multiply the current by the resistors value |
| mikerj:
--- Quote from: medical-nerd on June 21, 2018, 12:50:10 pm ---If I have a module that uses e.g 275mA at a supply of 5V, if there is a resistance of 10ohm after the voltage regulator, what is the voltage drop across the resistor? --- End quote --- At 275mA a 10 ohm resistor will drop 0.275*10=2.75volts. The problem here is that with the resistor in circuit your load is now only seeing 5-2.75=2.25v, so is unlikely to be taking 275mA any more (unless it's a constant current sink). Current sensing resistors usually have low values to minimise voltage drop, which may then require amplification to get a useful signal. |
| Audioguru:
--- Quote from: medical-nerd on June 21, 2018, 12:50:10 pm ---if there is a resistance of 10ohm after the voltage regulator --- End quote --- Is the 10 ohms resistor in series with the 275mA module? Then the module is not getting 5V and probably is not drawing 275mA anymore. |
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