The basic law describing the flow of electric current is Ohm’s law, which relates voltage (V) and current (I) to resistance (R): V=I x R
When measuring resistance in an electronic circuit you must first disconnect all voltage sources from the circuit whose resistance you want to measure. This is done because the multimeter will inject a known voltage into the circuit. In order to measure the resistance the switch must be closed (of it is open there will be no flow of current). So, according to these the following statements are true:
connect the multimeter between points C and D and measure the resistance with switch S1 closed.
D. connect the multimeter between points D and A and measure the resistance with switch S1 closed.
