The INCORRECT statement is
- The direction of eddy currents is given by Lenz' law.
- A choke coil is a pure inductor used for controlling current in an A.C. circuit.
- The r.m.s. value of A.C. current is √2 times the peak value of A.C. current.
- Quality factor is a measure of sharpness of resonance in A.C.circuit.
- Magnetic field energy stored in an inductor of inductance L is \(\frac{1}{2}LI^2\).
The Correct Option is C
Approach Solution - 1
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.
Approach Solution -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.
Top KEAM Physics Questions
- A body oscillates with SHM according to the equation (in SI units), $x = 5 cos \left(2\pi t +\frac{\pi}{4}\right) .$ Its instantaneous displacement at $t = 1$ second is
Kepler's second law (law of areas) of planetary motion leads to law of conservation of
- Two capillary tubes A and B of diameter $1\, mm$ and $2\, mm$ respectively are dipped vertically in a liquid. If the capillary rise in A is 6 cm, then the capillary rise in B is
- In the circuit given in figure, 1 and 2 are ammeters. Just after key K is pressed to complete the circuit, the reading will be
- A plate has a length $ 5\pm 0.1\text{ }cm $ and breadth $ 2\pm 0.01\text{ }cm $ . Then the area of the plate is:
Top KEAM Alternating current Questions
- A transformer has an efficiency of 80%. It is connected to a power input of $ 5 \,kW $ at $ 200\, V $ . If the secondary voltage is $ 250\, V $ , the primary and secondary currents are respectively
- A voltage $V_{PQ} = V_0 \, \cos \, \omega t$ (where $V_0$ is a real amplitude) is applied between the points P and Q in the network shown in the figure. The values of capacitance and inductance are $C = \frac{1}{\omega R \sqrt{3}}$ and $L = \frac{R \sqrt{3}}{\omega}$ Then, the total impedance between P and Q is
- An $LCR$ series $AC$ circuit is at resonance with $10\, V$ each across $L, C$ and $R$. If the resistance is halved, the respective voltages across $L, C$ and $R$ are
- An $LCR$ series circuit is at resonance. Then
- In a pure inductive AC circuit
Top KEAM Questions
- i.$\quad$ They help in respiration ii.$\quad$ They help in cell wall formation iii.$\quad$ They help in DNA replication iv. $\quad$They increase surface area of plasma membrane Which of the following prokaryotic structures has all the above roles?
- A body oscillates with SHM according to the equation (in SI units), $x = 5 cos \left(2\pi t +\frac{\pi}{4}\right) .$ Its instantaneous displacement at $t = 1$ second is
- The pH of a solution obtained by mixing 60 mL of 0.1 M BaOH solution at 40m of 0.15m HCI solution is
Kepler's second law (law of areas) of planetary motion leads to law of conservation of
- If $\int e^{2x}f' \left(x\right)dx =g \left(x\right)$, then $ \int\left(e^{2x}f\left(x\right) + e^{2x} f' \left(x\right)\right)dx =$