Question

In the following circuit diagram, if the diode is ideal, what is the value recorded by the ammeter?

A) Zero
B) \[0.25\]
C) $0.5$
D) $0.75$

Answer 1

Hint: Ideal diode behaves like a perfect conductor and the current is proportional to the applied voltage over a wide range. Its resistance is equal to the reciprocal of the slope of the line, is constant.

Formula used:
Ohm’s law, $V = IR$, where $V$=voltage across the circuit, $I$= current flow across the circuit, $R$=Resistance of the resistors.

Complete step by step solution:
 Let us consider the diagram that is given in the question. The ammeter is connected to a circuit to calculate the current flow through it. The ammeter is connected in series combination with the circuit. The voltmeter is connected in parallel combination to the circuit to calculate the voltage across the circuit as voltage remains the same in parallel branches.
 The diode is ideal. So, there is no voltage drop across it.
 $5V = 10I + 10I$
 After the addition of the current values,
 $ \Rightarrow 5 = 20I$
 $ \Rightarrow I = \dfrac{5}{{20}}A$
 $\therefore I = 0.25A$

Hence the correct option is (B).
Additional information:
There are actually two ways to measure the current that is flowing through the circuit. One is by an ammeter and another method is by a voltmeter. Both are electrical instruments and have a major difference between them. For an ideal ammeter, the value of resistance is zero. Changing the range is not possible. For the ideal voltmeter, the value of resistance approximately tends to infinity. Changing of range in the voltmeter is possible.

Note:
1. The ideal diode does not have a threshold voltage. Once any forward voltage is applied across the diode, it will conduct current instantly across its junctions.
2. Ideal diode does not have breakdown voltage; this is because the diode has unlimited resistance to reverse voltage.
3. The key function of an ideal diode is to control the direction of the current flow.
4. Current trying to flow if the reverse direction is blocked.
5. The ideal curve of $I$-$V$ represents a nonlinear resistance as same as an ideal diode.