EMI +AC +EM waves - live session - 29 Aug Contact Number: 9667591930 / 8527521718

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The figure shows the variation of \(R\), \(X_L\), and \(X_C\) with frequency \(f\) in a series of \(L\), \(C\), and \(R\) circuits. For which frequency point is the circuit inductive?

1. | \(A\) | 2. | \(B\) |

3. | \(C\) | 4. | All points |

Consider now the following statements

I. | Readings in \(A\) and \(V_2\) are always in phase |

II. | Reading in \(V_1\) is ahead in phase with reading in \(V_2\) |

III. | Readings in \(A\) and \(V_1\) are always in phase |

1. | I only | 2. | II only |

3. | I and II only | 4. | II and III only |

A thin semicircular conducting ring (PQR) of radius 'r' is falling with its plane vertical in a horizontal magnetic field B, as shown in figure. The potential difference developed across the ring when its speed is v is:

1. Zero

2. $Bv{\mathrm{\pi r}}^{2}/2$ and P is at the higher potential

3. $\mathrm{\pi rBv}$ and R is at the higher potential

4. 2BvR and R is at the higher potential

A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate $\frac{dB}{dt}$. Loop 1 of radius R > r encloses the region r and loop 2 of radius R is outside the region of the magnetic field as shown in the figure. Then, the emf generated is:

1. Zero in loop 1 and zero loop 2

2. $-\frac{dB}{dt}\pi {r}^{2}$ in loop 1 and zero in loop 2

3. $-\frac{dB}{dt}\pi {R}^{2}$ in loop 1 and zero in loop 2

4. Zero in loop 1 and not defined in loop 2

The key K is inserted at time t= 0. The initial (t=0) and final $\left(t\to \infty \right)$ currents through battery are :

1. $\frac{1}{15}Amp,\frac{1}{10}Amp$

2. $\frac{1}{10}Amp,\frac{1}{15}Amp$

3. $\frac{2}{15}Amp,\frac{1}{10}Amp$

4. $\frac{1}{15}Amp,\frac{2}{25}Amp$

An electron moves on a straight-line path XY as shown. The abcd is a coil adjacent to the path of electrons. What will be the direction of current if any, induced in the coil?

,

1. abcd

2. adcb

3. The current will reverse its direction as the electron goes past the coil

4. No current included

The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux ϕ linked with the primary coil is given by ϕ=${\varphi}_{0}$+4*t*, where ϕ is in weber, *t* is time in second and ϕ_{0}is a constant, the output voltage across the secondary coil is:

1. 90 V

2. 120 V

3. 220 V

4. 30 V

While keeping area of cross-section of a solenoid same, the number of turns and length of solenoid one both doubled. The self inductance of the coil will be

1. halved

2. doubled

3. $\frac{1}{4}$ times the original value

4. unaffected

For a transparent medium, relative permeability and permittivity,\(\mu_r~\text{and}~\varepsilon_r\) are \(1.0\) and \(1.44\) respectively. The velocity of light in this medium would be:

1. \(2.5\times10^{8}~\text{m/s}\)

2. \(3\times10^{8}~\text{m/s}\)

3. \(2.08\times10^{8}~\text{m/s}\)

4. \(4.32\times10^{8}~\text{m/s}\)

The intensity of visible radiation at a distance of 1 m from a bulb of 100 W which converts only 5% its power into light is :

(1) 0.4 $W/{m}^{2}$ (2) 0.5 $W/{m}^{2}$

(3) 0.1 $W/{m}^{2}$ (4) 0.01 $W/{m}^{2}$

The charge of a parallel plate capacitor is varying as $q={q}_{0}\mathrm{sin}\omega t$. Then find the magnitude of displacement current through the capacitor. (Plate Area = A, separation of plates = d)

(1) ${q}_{0}\mathrm{cos}\left(\omega t\right)$ (2) ${q}_{0}\omega \mathrm{sin}\omega t$

(3) ${q}_{0}\omega \mathrm{cos}\omega t$ (4) $\frac{{q}_{0}A\omega}{d}\mathrm{cos}\omega t$

The energy density of the electromagnetic wave in vacuum is given by the relation

(1) $\frac{1}{2}.\frac{{E}^{2}}{{\epsilon}_{0}}+\frac{{B}^{2}}{2{\mu}_{0}}$ (2) $\frac{1}{2}{\epsilon}_{0}{E}^{2}+\frac{1}{2}{\mu}_{0}{B}^{2}$

(3) $\frac{{E}^{2}+{B}^{2}}{C}$ (4) $\frac{1}{2}{\epsilon}_{0}{E}^{2}+\frac{{B}^{2}}{2{\mu}_{0}}$

An inductor 20 mH, a capacitor 100 μF, and a resistor 50 $\Omega $ are connected in series across a source of emf, V= 10sin314t. The power loss in the circuit is:

1. 0.79 W

2. 0.43 W

3. 2.74 W

4. 1.13 W

1. | When the capacitor is air-filled. |

2. | When the capacitor is mica filled. |

If the current through the resistor is \(I\) and the voltage across the capacitor is \(V\), then:

1. \(V_a < V_b\)

2. \(V_a > V_b\)

3. \(i_a > i_b\)

4. \(V_a = V_b\)

In a certain circuit current changes with time according to $\mathrm{i}=2\sqrt{\mathrm{t}}$. Root mean square value of current between t=2 to t=4s will be:-

1. $\sqrt{2}\mathrm{A}$

2. $2\mathrm{A}$

3. $2\sqrt{3}\mathrm{A}$

4. $130\mathrm{V}$

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