Suppose the `19 Omega` resistor of the previous problem is disconnected. Find the current through `P_2 Q_2` in the two situations (a) and (b) of that problem.

Options

A. zero
B. 3 mA
C. 1 mA
D. None of these

Answer

To solve the problem, we need to analyze the circuit after disconnecting the 19 ohm resistor and find the current through points P2 and Q2 in both situations (a) and (b) as described in the previous problem.

### Step-by-Step Solution:

1. **Understanding the Circuit Configuration**:
- We have a circuit with resistors and points P1, P2, Q1, and Q2.
- The 19 ohm resistor is disconnected, which may affect the current flow in the circuit.

2. **Analyzing Situation (a)**:
- In situation (a), it is mentioned that the circuit is incomplete. This implies that there is no closed loop for current to flow.
- Since the circuit is open, the current through P2Q2 will be **0 A**.

3. **Analyzing Situation (b)**:
- In situation (b), the circuit is complete, and we can calculate the current through P2Q2.
- We assume that there are two 2 ohm resistors in parallel connected to a voltage source (let's say V).
- The equivalent resistance (R_eq) of two 2 ohm resistors in parallel is given by:
\[ R_{eq} = \frac{1}{\frac{1}{2} + \frac{1}{2}} = 1 \text{ ohm} \]

4. **Calculating the Current**:
- If the voltage across the circuit is V (let's assume V = 1V for calculation), the current (I) through the equivalent resistance can be calculated using Ohm's Law:
\[ I = \frac{V}{R_{eq}} = \frac{1V}{1 \text{ ohm}} = 1 \text{ A} \]
- Therefore, the current through P2Q2 in situation (b) is **1 A**.

### Final Answers:
- For situation (a): Current through P2Q2 = **0 A**
- For situation (b): Current through P2Q2 = **1 A**