Question

Which of the following statements is not true for electric energy in ac form compared to that in dc form?

• A. Production of ac is economical.
• B. ac can be easily and efficiently converted from one voltage to the other.
• C. ac can be transmitted economically over long distances.
• D. ac is less dangerous.

Hint:

AC peak voltage is \(\sqrt{2} \times V_{rms}\). For a 220V supply, the peak is actually 311V, which is one reason why it's more hazardous than 220V DC.

Answer 1

The Correct Option is D

To address the question regarding comparing electric energy in AC and DC forms, let's evaluate each given statement to identify which one is not true:

1. Production of AC is economical:

   AC is generally more economical to produce than DC. Most power plants generate AC because it can be easily generated by rotating machinery like turbines and alternators. Therefore, this statement is true.

2. AC can be easily and efficiently converted from one voltage to the other:

   One of the major advantages of AC over DC is its ability to change voltages using transformers, thus allowing high-voltage, low-current transmission over long distances, which reduces energy loss. Hence, this statement is true.

3. AC can be transmitted economically over long distances:

   As mentioned, AC can be transmitted at high voltages, which reduces energy loss and makes it economical for long-distance transmission. Therefore, this statement is true.

4. AC is less dangerous:

   AC is actually more dangerous to human safety than DC. AC has a higher possibility to cause ventricular fibrillation at common domestic frequencies (like 50-60 Hz). Thus, this statement is not true.

Conclusion: The statement that is not true for electric energy in AC form compared to DC form is: AC is less dangerous. This statement is incorrect because, in common circumstances, AC poses a higher risk than DC due to its characteristics and effects on the human body.