DC Theory, Lvl III, Lesson 2

For two resistors to be in parallel with each other in a circuit, there must be ? current path(s).

2

When resistors are connected in parallel, the total resistance of the circuit will be greater than the smallest resistor value in the circuit.

False

Adding additional resistors in parallel with those resistors already existing in a parallel connected circuit will always increase the total resistance.

False Note: Adding additional resistors in parallel with those resistors already existing in a parallel connected circuit will always decrease the total resistance.

What is the total circuit resistance with S1 and S3 closed? (Round the FINAL answer to two decimal places.)

RT = (R1 x R2)/(R1 + R2) = (270 x 470) / (270 +470) = 171.49

What is the total circuit resistance with S1 and S2 closed? (Round the FINAL answer to two decimal places.)

RT = (R1 x R2)/(R1 + R2) = (270 x 620) / (270 +620) = 188.09

What is the total circuit resistance with all switches closed? (Round the FINAL answer to two decimal places.)

RT = 1/((1/R1) + (1/R2) + (1/R3)) = 1/((1/270) + (1/620) + (1/470)) = 134.33

When can the reciprocal method be used to calculate total resistance in parallel circuits?

The reciprocal method can be used to calculate the total resistance of any combination of parallel resistances.

The total resistance of any number of parallel resistances, all having the same value, is equal to the value of any one of the resistors divided by the total number of resistors.

True

What is the total resistance of the circuit with S1 closed, and both S2 and S3 open?

With S1 closed and both S2 and S3 open, the only resistance seen by the source is R1. This is a simple series circuit. The resistance is 270 ohms.

With S1 open, what affect will it have on the circuit?

With S1 open, the source is disconnected from the resistors since S1 open is in series with the source; therefore, no current would flow.