Question

The INCORRECT statement is

• A. The direction of eddy currents is given by Lenz' law.
• B. A choke coil is a pure inductor used for controlling current in an A.C. circuit.
• C. The r.m.s. value of A.C. current is √2 times the peak value of A.C. current.
• D. Quality factor is a measure of sharpness of resonance in A.C.circuit.
• E. Magnetic field energy stored in an inductor of inductance L is \(\frac{1}{2}LI^2\).

Answer 1

The Correct Option is C

The r.m.s. (root mean square) value of an A.C. current is related to the peak value of the current by the formula: \[ I_{\text{rms}} = \frac{I_{\text{peak}}}{\sqrt{2}} \] Thus, the r.m.s. value of A.C. current is \(\frac{1}{\sqrt{2}}\) times the peak value, not \(\sqrt{2}\) times.
Therefore, statement (C) is incorrect.

Other statements are correct:
(A) The direction of eddy currents is indeed governed by Lenz's law.
(B) A choke coil is a pure inductor used to control the current in A.C. circuits.
(D) The quality factor is a measure of the sharpness of resonance in A.C. circuits.
(E) The energy stored in an inductor is correctly given by \(\frac{1}{2} L I^2\).

The correct option is (C) : The r.m.s. value of A.C. current is \(\sqrt 2\) times the peak value of A.C. current.

Answer 2

Correct Option (INCORRECT statement): The r.m.s. value of A.C. current is √2 times the peak value of A.C. current. 
 
Explanation:

• This statement is incorrect.
• The r.m.s. (root mean square) value of an A.C. current is actually \(\frac{I_0}{\sqrt{2}}\), where \( I_0 \) is the peak current.
• So, the r.m.s. value is less than the peak value, not √2 times greater.

Final Answer: The r.m.s. value of A.C. current is √2 times the peak value of A.C. current.