In the circuit shown in the figure, find the value of the current shown in the ammeter A.
figure 1
to find the current shown in ammeter, find the current through 6 resistance. Here assume ammeter is ideal, so resistance of ammeter is is zero. The 4 resistance and 2 resisatnce are in series.
We know at series connection
parallel connection
So
The figure can be redrawn into
figure 2
and are parallel so effective resistance is
Then figure become
figure 3
9 and 3 are in series,
effective resistance is 9 + 3 = 12
Figure become,
figure 4
12 and 12 are in parallel so,
figure 5
3 and 6 are in series, so
3 + 6 = 9
By ohm's law,
In figure 4 both 12 resistance have current = 0.5A
The equivalent figure is,
from the above diagram, the current through 6 resistance is
Hence, the current shown in the ammeter is 0.25A,