Chapter 21, Problem 34PCE

Predict/Explain Two resistors are connected in parallel. (a) If a third resistor is now connected in parallel with the original two, does the equivalent resistance of the circuit increase, decrease, or remain the same? (b) Choose the best explanation from among the following:

1. I.        Adding a resistor generally tends to increase the resistance, but putting it in parallel tends to decrease the resistance; therefore the effects offset and the resistance stays the same.
2. II.      Adding more resistance to the circuit will increase the equivalent resistance.
3. III.   The third resistor gives yet another path for current to flow in the circuit, which means that the equivalent resistance is less.