You would be drawing more current. It would be the same as adding more load to the circuit in a vehicle, say more lights. The lights would just be seen as more load (a resistive load in the case of incandescent lights). Add more lights (resistors) and more current is needed. The ammeter would indicate a higher current draw.
decrease to half of its original value
Connect ammeter in series and voltmeter in parallel to the circuit
The voltage remains the same across the circuit as it is a parallel connection. So, the current across the upper half of the circuit where the ammeter is connected is calculated as I = V/R = 12.04 (total voltage)/12 (Resistance R1) = 1 A. Hence, the ammeter will read 1 A.
In a circuit with three cells, the ammeter reading will depend on how the cells are connected. If they are connected in series, the total voltage increases, which can lead to a higher current, assuming resistance remains constant. If they are connected in parallel, the voltage remains the same as a single cell, but the total current could increase due to the combined capacity of the cells. Therefore, the ammeter's reading will vary based on the configuration of the cells.
the bulb will glow and ammeter will show the reading
The Positive side of the Ammeter should be connected to the positive side of the battery and the Negative side should be connected to the Globe/Conductor/Insulator to provide a valid reading.
Ammeters have a low impedance, so if they are incorrectly connected in parallel to your load instead of in series, more current will flow through the circuit and the ammeter will almost act like a short. There is potential to burn our the ammeter.
You'll get a reading on the ammeter showing 15 mA
Connecting an ammeter does not reduce the frequency errors.
Assuming the new lamp is in series, the ammeter reading falls because the total resistance has increased. By how much depends on how the lamp resistance depends on voltage. If the lamp is added in parallel to the first, then the ammeter reading doubles.
Two ways to connect an ammeter, You can use a direct reading type, by connecting the ammeter in series with the load. You can use a current transformer type or CT. The current transformer looks like a wire wrapped donut with two terminals on its side with a hole through the middle. you pass the wire carrying the load through the center. Connect the direct reading meter to the two terminals. A CT type meter allows you to measure higher currents.
If the amp meter is in series ahead of the first parallel branch of lamps the meter will read an increase in current.