Please explain clearly Thank you Chegg experts The circuit b

The circuit below uses a switch and a transistor to switch a light bulb on or off. (a) Which setting of the switch turns off the light? Justify your answer (b) Which setting of the switch turns on the light? Justify your answer (c) In the \"on\" configuration, why would the transistor probably be runed if the resistor R_b is taken out?

Solution

if S is connected to A then the bulb glows

The base resistor is chosen small enough so that the base current drives the transistor into saturation.

In this example the mechanical switch is used to produce the base current to close the transistor switch to show the principles. In practice, any voltage on the base sufficient to drive the transistor to saturation will close the switch and light the bulb.

when the S is connected to B ,the bulb gets off

There is no current to the base, so the transistor is in the cut off condition with no collector current. All the voltage drop is accoss the transistor

yes the transister would probably ruined if the resistance is not present

A resistor is a passive two-terminal electrical component that implements electrical resistance as acircuit element. Resistors may be used to reduce current flow, and, at the same time, may act to lower voltage levels within circuits

it can lower the current and voltage levels

excess of volatge and current levels leads to burning of the components in the circuit