Find the total current in the circuits shown in Fig. , , and . Each diode used is ideal

Explanation

In Fig. , both the diode
`D_(1)` and `D_(2)` are forward biased. Their effective
resistance in current is zero. Current in circuit is
`I=3.0/10=0.3A`
In Fig., diode `D_(1)` is forward bias and diode `D_(2)` is reverse biased. Resistance due to `D_(2)` will be infinity to the current flowing through it. So
Current in the circuit, `I=(3.0)/(10+oo)=0`
In Fig. , both the diode `D_(1)` and `D_(2)` are forward biased, Their effective resistance in the circuit is zero. So Current in the circuit is
`I=3.0/10=0.3A`
In Fig. , diode `D_(1)` is forward biased and diode `D_(2)` is reverse biased. No current will flow through `D_(2)` as its resistance become infinity being reverse biased. The resistance to current by `D_(1)` is zero. The current in the circuit is due to `D_(1)` only, which is given by
`I=3.0/10=0.3A`