A zener diode used as voltage regulator is connected (i) in forward bias (ii) in reverse bias (iii) in parallel with load (iv) in series with load (A) (i) and (ii) are correct (B) (ii) and (iii) are correct (C) only (i) is correct (D) only (iv) is correct

A Zener diode is a special diode that allows current to flow in the reverse direction when a certain "Zener voltage" is reached. When used as a voltage regulator, it maintains a constant voltage across the load, regardless of changes in the input voltage or load current.

In the forward bias condition, a diode allows current to flow in the direction of its arrow and acts like a typical diode. A Zener diode doesn't act like a voltage regulator in forward bias mode. Instead, it acts like a regular diode, passing current through when the input voltage is above the threshold level. So, the statement (i) is not correct for the functioning of a Zener diode as a voltage regulator.

When a diode is reverse biased, it does not allow current to flow until its breakdown voltage is reached. For a Zener diode, this breakdown voltage is not destructive, and the diode continues to work as a regulator at this point. Once the breakdown voltage is reached, the Zener diode maintains a constant voltage across the load. So, the statement (ii) is correct for the functioning of a Zener diode as a voltage regulator.

When a Zener diode is connected in parallel with the load, the input voltage is shared between the diode and the load. If the input voltage increases, more current will flow through the Zener diode, but the voltage across the load will remain constant. Conversely, if the input voltage decreases, less current will flow through the Zener diode, protecting the load from voltage drops. So, the statement (iii) is correct for the functioning of a Zener diode as a voltage regulator.

When a Zener diode is connected in series with the load, it cannot regulate the voltage across the load, since the entire current either flows through the diode and the load or doesn't flow at all. In this configuration, the Zener diode doesn't function as a voltage regulator; thus, statement (iv) is not correct for the functioning of a Zener diode as a voltage regulator. From our analysis of the statements: (A) (i) and (ii) are correct - Incorrect, we concluded that only (ii) is correct. (B) (ii) and (iii) are correct - Correct, we concluded that both (ii) and (iii) are correct. (C) only (i) is correct - Incorrect, we concluded that (i) is not correct. (D) only (iv) is correct - Incorrect, we concluded that (iv) is not correct. Therefore, the correct answer is (B) (ii) and (iii) are correct.