Capacitor in an AC Circuit

Q. There are four identical metal plates each of area $A$. The plates are placed at equal distance $d$ successively as shown in figure. If $\frac{A{ϵ}_0}{d}=2\mu F$ and source of emf $10V$ is connected between $x$ and $y$, then charge on plate $x$ will be

1. $+20\mu C$
2. $-20\mu C$
3. $-30\mu C$
4. $+30\mu C$

Q. An inductor of inductance $20mH$, a capacitor of capacitance $100\mu F$ and a resistor of resistance $50\Omega$ are connected in series across a source of emf, $V=10\sin \left(314t\right)$. The power loss in the circuit is

1. $0.79W$
2. $0.43W$
3. $2.74W$
4. $1.13W$

Q.

What are three applications of capacitors in circuits?

Q.

The electronic components used in the third generation of computers are

1. Vacuum tubes

2. Transistors

3. Integrated circuit

4. None of these

Q. What is the physical significance of quality factor and the sharpness in AC circuit ???please explain in detail

Q.

The reading of the ammeter and voltmeter in the following circuit respectively are

1. 2 A, 200 V

2. 1.5 A, 100 V

3. 2.7 A, 220 V

4. 2.2 A, 220 V

Q. 10. An ideal choke draws a current of 8 A when connected to an AC supply of 100 V, 50 Hz. A pure resistor draws a current of 10 A when connected in series and then connected in series and then connected to the AC source of 150 , 40 Hz. The current in the circuit becomes (a) 15/2*1/2 A [i.e. 15 upon root 2] (b) 8 A (c) 18 A (d) 10 A

Q.

Why do capacitors oppose the change in voltage?

Q.

Should a capacitor have continuity?

Q. Two capacitors having capacitors $C_1\text{and}{C}_2$ respectively are connected as shown in figure. Initially, capacitor $C_1$ is charged to a potential difference $\text{V}$ volt by a battery. The battery is then removed and the charged capacitor $C_1$ is now connected to uncharged capacitor $C_2$ by closing the switch $S$. The amount of charge on the capacitor $C_2$, after equilibrium is

1. $(C_1+C_2)V$
2. $\frac{C_1{C}_2}{(C_1+C_2)}V$
3. $(C_1-C_2)V$
4. $\frac{(C_1+C_2)}{C_1{C}_2}V$

Q. Four identical resistors each of resis†an ce 2Ω are connected to battery of 20V and internal resis†an ce 2Ω. The reading of ideal ammeteri

Q. What is the value of shunt which passes $10\%$ of the main current through a galvanometer of $99\Omega$ ?

1. $25\Omega$
2. $50\Omega$
3. $11\Omega$
4. $15\Omega$

Q. In an a.c. circuit, resistance of $R\Omega$ is connected in series with an inductance $L.$ If phase angle between voltage and current be ${45}^{\circ }.$ The value of inductive reactance is-

1. $\frac{R}{4}$
2. $\frac{R}{2}$
3. $R$
4. $\sqrt{3}R$

Q. Pls Explain:for a transistor amplifier the voltage gain is low at high and low frequencies and constant at mid frequencies?

Q. Three capacitors are connected as shown in figure. Then the charge on capacitor plate $C_1$ is:

1. $6\mu C$
2. $12\mu C$
3. $18\mu C$
4. $24\mu C$

Q. An $AC$ circuit is shown in the figure. A dielectric slab is placed between the plates, then

1. Brightness of bulb increases.
2. Brightness of bulb decreases.
3. cannot say.
4. Brightness of buld remains same.

Q.

When current flows anticlockwise in a loop, the magnetic polarity of the face is

1. east

2. west

3. north

4. south

Q.

Why we use polarized capacitor?

Q.

The physical quantity which is not a unit of energy is

1. $volt-coulomb$

2. $MeV-s$

3. $henry{\left(ampere\right)}^2$

4. $farad-{\left(volt\right)}^2$

Q.

A coil of inductance 0.5 h and a resistor of resistance 100ω are connected in series to a 240v, 50 hz supply. (a) find the maximum current in the circuit (b) what is the time lag between voltage maximum and current maximum?

Q. Is the voltage gain of common emitter amplifier constant, irrespective of magnitude of the input signal?

Q.

If we change the value of $R$, then

1. Voltage does not change on $C$

2. Voltage does not change on $L$

3. Voltage change on $LC$ combination

4. Voltage does not change on $LC$ combination

Q. A 2V battery, a $990\Omega$ resistor and a potentiometer of 2m length, all are connected in series, the resistance of potentiometer wire is $10\Omega$, then the potential gradient of potentiometer wire is:

1. 0.1 V/m
2. 0.5 V/m
3. 0.01 V/m
4. 0.05 Vm

Q. 77. Assertion-:Average of sinusoidal AC can never be zero over half cycle. Reason-:impedance of inductor does not depend upon frequency

Q.
In a given circuit, switch S was closed for a long time and is opened in an instant. Charge on capacitor after time $t=\frac{\pi }{1200}sec$ after opening the switch is

1. $1.73mC$
2. $14.1mC$
3. $10mC$
4. $5mC$

Q. The power factor of a circuit in which a box having unknown electrical devices connected in series with a resistor of resistance $3\Omega$ is $\frac{3}{5}$. The reactance of the box is

1. $5\Omega$
2. $\frac{5}{3}\Omega$
3. $4\Omega$
4. $\frac{4}{3}\Omega$

Q.

A choke coil is needed to operate an arc lamp at 160V (RMS) and 50Hz. The arc lamp has an effective resistance of 5Ω when running at 10A (rms). Calculate the inductance of the choke coil. If the same arc lamp is to be operated on 160V DC, what additional resistance would be required. Compare the power losses in both the cases.

Q. When a current of $100\mu \text{A}$ is passed through a galvanometer, it gives a full deflection of $50\text{divisions}$. If resistance of galvanometer is $1000\Omega$, its voltage semitivity is

1. $500\text{div/V}$
2. $500\text{div/mV}$
3. $5\text{div/V}$
4. $5\text{div/mV}$

Q. A string is stretched between fixed points separated by $75.0\text{cm}$. It is observed to have resonant frequencies of $420\text{Hz}$ and $315\text{Hz}$. There are no other resonant frequencies between these two. The lowest resonant frequency for this string is

1. $10.5\text{Hz}$
2. $105\text{Hz}$
3. $155\text{Hz}$
4. $205\text{Hz}$

Q.

Transistors are useful in equipments such as hearing aids and small radio receivers because transistors :

1. Consume little power

2. Are inexpensive

3. do not distort sound

4. Can stand rough use