Resistance in a DC Circuit.

What would be the correct formula to use to calculate the value of a variable resistor in a DC circuit?
- Dorothy (age 32)
Papua New Guinea

The relationship between voltage, current, and resistance is  V = I R.   So you need to measure the current with an ammeter and the voltage with a voltmeter.   You can do this with these instruments imbedded in the circuit or just take the resistor out of the circuit and measure its resistance with a simple ohmmeter.  The ohmmeter is nothing more than a fixed voltage that is applied to the resistance and an internal ammeter that measures the current, or (more commonly) an internal current source and a voltmeter to measure the voltage on the resistor.  Same result.

LeeH 

(published on 11/08/2011)