In the partial schematic above, what is the correct polarity of the grid current meter, Ig?

From top to bottom: - , +

From top to bottom: + , -

Grid current meter is in the wrong place, so it doesn't matter!

Answer: From top to bottom: - , +......negative meter terminal toward the grid. Significant grid current flows only when the positive RF input peaks exceed the grid bias. The grid collects some electrons as they pass from cathode to anode. The electrons have to flow from the grid back to the cathode or else the grid voltage would keep going more and more negative as the electrons piled up!