Analog Electronics
The encapsulation of transistor is necessary for

Mechanical ruggedness
Preventing photo-emission effects
Avoiding loss of free electrons
Preventing radio interference

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Analog Electronics
The arrowhead on the transistor symbol points in the direction of

  electron flow in the emitter region.
  minority carrier flow in the emitter region.
  conventional electric current flow in the emitter region.
  majority carrier flow in the emitter region.

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