Which of the following statement(s) is/are correct?

Options

A. A capacitor acts as an infinite resistance for AC as well as DC current.
B. An electric transformer can step up or step down the AC as well as DC voltage.
C. Hot wire ammeter and voltmeter can measure current and voltage, respectively, both for AC and DC voltages.
D. We use a choke coil in series with a tube light to reduce voltage across the tube light, without losing electrical energy in the form of heat as an ideal inductor does not consume power in a circuit.

Answer

To determine which of the statements regarding capacitors, transformers, and measurement devices are correct, let's analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement 1: Capacitor acts as an infinite resistance for AC as well as DC current.**
- For DC current, the frequency (ω) is 0. The capacitive reactance (Xc) is given by the formula \( X_c = \frac{1}{\omega C} \). Since ω = 0 for DC, Xc tends to infinity, meaning the capacitor blocks DC current.
- For AC current, ω is greater than 0, which means Xc has a finite value. Therefore, a capacitor does not act as an infinite resistance for AC.
- **Conclusion**: This statement is **incorrect**.

2. **Statement 2: An electrical transformer can step up or step down AC as well as DC Voltage.**
- A transformer operates based on the principle of electromagnetic induction, which requires a changing magnetic field. This is only possible with AC, as DC provides a constant current and does not induce a changing magnetic field.
- Therefore, transformers cannot operate with DC voltage.
- **Conclusion**: This statement is **incorrect**.

3. **Statement 3: Hot wire ammeter and voltmeter can measure current and voltage respectively both for AC and DC voltage.**
- A hot wire ammeter measures the heat generated by the current flowing through it, which can be done for both AC and DC currents. It measures the RMS value of the current.
- A voltmeter typically measures voltage, but standard voltmeters are designed for AC or DC specifically. However, hot wire ammeters are capable of measuring both.
- **Conclusion**: This statement is **correct**.

4. **Statement 4: We use a choke coil in series with a tube light to reduce voltage across the tube light without losing electrical energy in the form of heat as well as an ideal inductor does not consume power in a circuit.**
- A choke coil (inductor) is used to limit the current in AC circuits. It creates a phase difference between voltage and current, ideally leading to zero power consumption (cos φ = 0).
- The inductor does not dissipate energy as heat; instead, it stores energy temporarily in its magnetic field.
- **Conclusion**: This statement is **correct**.

### Final Answer:
- The correct statements are **3 and 4**.