Table of Contents
Ans. (c) 7 A
Explanation:
\because \space \space \space \space \space \mathrm{I}_{\mathrm{mms}} =\dfrac{\mathrm{E}_{\mathrm{mms}}}{\mathrm{R}} \\[4.5 bp]
=\dfrac{200}{40} \\[4.5 bp]
=5 \mathrm{~A} \\[4.5 bp]
\therefore \space \space \space \space \space \mathrm{I}_{0} =\mathrm{I}_{\mathrm{rms}} \sqrt{2} \\[4.5 bp]
=7.07 \mathrm{~A}
Ans. (c) L is large and R is small
Explanation: Since, selectivity depends on the quality of resonance. The quality factor is given by \text{Q = Ω}_o\text{L/R} . High value of quality factor make sure that the resonance curve is sharp, sharper the resonance curve, more selective is the LCR circuit.
Explanation:
The phase difference between the voltage and current in an AC circuit refers to the time delay or phase shift between the two waveforms. In an AC circuit, the voltage and current are not always in phase due to the presence of reactive elements like inductors and capacitors. The phase difference is represented by the angle ϕ.
The power factor (PF) of an AC circuit is defined as the cosine of the angle f. It represents the ratio of the real power (P) to the apparent power (S) in the circuit. The power factor indicates how effectively the circuit utilizes the supplied power. A power factor of 1 (or unity) means that the voltage and current are in phase, resulting in maximum power transfer.
Explanation:
The glow of the bulb will remain unchanged, if the current through the bulb does not change. It will happen so, if the impedance of the circuit remains unchanged. The impedance of the LCR circuit is given by \\ \text{Z} = \sqrt{\text{R}^2 + \left(2 \pi\text{fL} - \dfrac{1}{2\pi \text{fC}}\right)^2} \\
It follows that when f is doubled, Z will remain unchanged, if the values of both L and C are halved.
Explanation:
A transformer works on a.c. supply. Therefore, during its operation, the iron core of the transformer is taken over the complete cycle of magnetisation and demagnetisation again and again. In taking the core over a complete cycle of magnetisation, the energy spent per unit volume of the core is equal to area of the hysteresis loop. Therefore, to minimise the loss of energy, the core of the transformer is made of a material, whose hysteresis loop is narrow.
| Chapter No. | Chapter Name |
|---|---|
| Chapter 1 | Electric Charges and Fields |
| Chapter 2 | Electrostatic Potential and Capacitance |
| Chapter 3 | Current Electricity |
| Chapter 4 | Moving Charges and Magnetism |
| Chapter 5 | Magnetism and Matter |
| Chapter 6 | Electromagnetic Induction |
| Chapter 7 | Alternating current |
| Chapter 8 | Electromagnetic Waves |
| Chapter 9 | Ray Optics and Optical Instruments |
| Chapter 10 | Wave Optics |
| Chapter 11 | Dual Nature of Radiation and Matter |
| Chapter 12 | Atoms |
| Chapter 13 | Nuclei |
| Chapter 14 | Semiconductor Electronics: Materials, Devices and Simple Circuits |
| Chapter Wise Important Questions for CBSE Board Class 12 Physics |
|---|
| Electric Charges and Fields |
| Electrostatic Potential and Capacitance |
| Current Electricity |
| Moving Charges and Magnetism |
| Magnetism and Matter |
| Electromagnetic Induction |
| Alternating current |
| Electromagnetic Waves |
| Ray Optics and Optical Instruments |
| Wave Optics |
| Dual Nature of Radiation and Matter |
| Atoms |
| Nuclei |
| Semiconductor Electronics: Materials, Devices and Simple Circuits |
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