A working transitor with its three legs marked `P, Q and R` is tested using a multimeter No conduction is found between `'P', Q `by connecting the common (negative) terminal of the multimeter to `R`and the other (positive) terminal to P or `Q` some resistance is seen on the multimeter . Which of the following is true for the transistor ?

Options

A. It is an n-p-n transistor with R as base
B. It is an p-n-p transistor with R as collector
C. It is an p-n-p transistor with R as emitter
D. It is an n-p-n transistor with R as collector

Answer

To solve the problem regarding the transistor with legs marked P, Q, and R, we need to analyze the information given about the conduction between the legs when tested with a multimeter. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Configuration of the Transistor
A transistor has three terminals: the emitter, base, and collector. We need to determine which terminal corresponds to P, Q, and R.

### Step 2: Analyze the Given Information
We know that there is no conduction between P and Q when the negative terminal of the multimeter is connected to R. This indicates that P and Q are not directly connected through a conductive path.

### Step 3: Understand the Implications of No Conduction Between P and Q
Since there is no conduction between P and Q, it suggests that one of these terminals (either P or Q) is likely the emitter or collector, while the other is the base. This means that PR and QR must have some conduction.

### Step 4: Determine the Role of Terminal R
With R being the common terminal for the negative connection, and observing some resistance when the positive terminal is connected to either P or Q, we can conclude that R is likely the base terminal. This is because the base-emitter junction is forward-biased when the positive terminal is connected to the emitter (either P or Q).

### Step 5: Conclude the Type of Transistor
Given that R is the base terminal and there is a high resistance observed when connecting the multimeter in reverse bias (negative to R), we can conclude that the transistor is an NPN type. In an NPN transistor, the base (R) is connected to the negative terminal, allowing for the emitter (either P or Q) to be forward-biased.

### Step 6: Final Conclusion
Thus, we can conclude that the correct option is that R is the base terminal of an NPN transistor.

### Summary of the Solution
- No conduction between P and Q indicates that one is likely the emitter and the other the collector.
- R is the base terminal.
- The transistor is an NPN type.