With the positive probe on an NPN base, an ohmmeter reading between th...
Explanation:
When an ohmmeter is connected to an NPN transistor with the positive probe on the base terminal, the reading between the other transistor terminals (collector and emitter) should be low resistance. This can be explained as follows:
1. NPN Transistor Structure:
An NPN transistor consists of three layers of semiconductor material: the emitter, base, and collector. These layers are doped with different types of impurities to create two pn junctions: the base-emitter junction (BE junction) and the base-collector junction (BC junction).
2. Base-Emitter Junction:
The base-emitter junction is forward-biased when a positive voltage is applied to the base terminal with respect to the emitter. This forward bias allows current to flow from the emitter to the base. The forward bias voltage causes the electrons from the emitter to move towards the base, creating a flow of majority charge carriers (electrons) through the base-emitter junction.
3. Base-Collector Junction:
The base-collector junction is reverse-biased when a positive voltage is applied to the collector terminal with respect to the base. This reverse bias prevents current flow through the base-collector junction. However, a small amount of current flows due to minority charge carriers (holes) from the base region being swept into the collector region.
4. Ohmmeter Reading:
When the positive probe of the ohmmeter is connected to the base terminal, it applies a positive voltage to the base with respect to the other transistor terminals.
- Collector-Emitter Reading: The collector-emitter junction is reverse-biased, so the ohmmeter reading between these terminals should be high resistance or open. This is because the reverse bias prevents current flow through the base-collector junction, and the ohmmeter measures the resistance between the collector and emitter.
- Base-Emitter Reading: The base-emitter junction is forward-biased, so the ohmmeter reading between these terminals should be low resistance. This is because the forward bias allows current flow through the base-emitter junction, and the ohmmeter measures the resistance between the base and emitter.
Therefore, when an ohmmeter is connected to an NPN transistor with the positive probe on the base terminal, the reading between the other transistor terminals should be low resistance. This indicates that the base-emitter junction is conducting, while the base-collector junction is not conducting.
With the positive probe on an NPN base, an ohmmeter reading between th...
Correct answer is C