In recent experiments, you worked with the NPN transistor BC 547 B. Here you get to know the PNP transistor BC 557 B.
The BC 557 B is the complementary transistor to the BC 547 B. To the outside you see no difference. However a PNP transistor is connected differently.
Consider the circuit shown. The base is connected via the resistor R1 to the positive terminal of the battery (+ 9 V). The PNP transistor is closed. (An NPN transistor in this circuit would switch through)
In the next experiment you switch through the PNP transistor.