Question

1. a parallel branch that has a changed value component

allows no current
changes ( z _ { t } , i _ { t } ), and voltage drops
eliminates the effect of the changed value component
measures the applied voltage across the changed value component

Explanation:

In a parallel - circuit, the voltage across each branch is the same (equal to the source voltage). The total impedance \(Z_T\) of a parallel circuit is given by \(\frac{1}{Z_T}=\sum\frac{1}{Z_i}\). If a component value (and thus its impedance \(Z_i\)) in one branch changes:

• The total impedance \(Z_T\) changes because of the formula for parallel - impedance.
• According to Ohm's law \(I_T=\frac{V}{Z_T}\), since \(Z_T\) changes and \(V\) (source voltage) is constant (assuming ideal source), the total current \(I_T\) changes.
• The voltage across each branch is equal to the source voltage (in a parallel circuit with an ideal source), so the voltage drop across each branch does not change. But the current through the branch with the changed component (by Ohm's law \(I = \frac{V}{Z}\), where \(V\) is constant and \(Z\) changes) and the total current \(I_T\) change.

• Option (a) is wrong because in a parallel circuit (unless the component is open - circuited), current will flow through the branch.
• Option (c) is wrong because changing a component value in a parallel branch does not eliminate its effect.
• Option (d) is wrong because in a parallel circuit with an ideal source, the voltage across each branch is the source voltage (a measured value would be related to the source, not just the component).

Answer:

B. changes \(Z_T\), \(I_T\), and voltage drops