Alternating Current Test

Result

Alternating Current Test - 23

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

The capacitive reactance in an AC circuit is

A
effective resistance due to capacity

B
effective wattage

C
effective voltage

D
None of these

Solution

Capacitive reactance in an A.C circuit is: $${X}_{C}=\cfrac{1}{\omega

C}$$ ohm
where, $$C$$ is the capacitance of capacitor and $$\omega=2\pi

n$$ ($$n$$ is the frequency of A.C source)
Question 2
1 / -0

If the inductance of a coil in 1 henry then its effective resistance in a $$D.C$$ circuit will be

A
$$\displaystyle \infty$$

B
zero

C
1 $$\Omega$$

D
2 $$\Omega$$

Solution

$${ X }_{ L }=\omega L$$
In DC, $$\omega=0$$
Therefore, effective inductive resistance is
$${ X }_{ L }=0$$
Question 3
1 / -0

The power loss in an $$AC$$ circuit is $$E_{rms}$$ $$I_{rms}$$, when in the circuit there is only

A
$$C$$

B
$$L$$

C
$$R$$

D
$$L,\ C$$ and $$R$$

Solution

Inductors and capacitors bring a phase difference between the voltage and current in the circuit, hence changing the p.f. When only a resistance is present, $$Poer\ factor= 1$$.
The power loss in an AC circuit$$ =E_{rms} I_{rms} Power\ factor $$
Question 4
1 / -0

With increase in frequency of an A.C. supply, the inductive reactance

A
decreases

B
increases directly with frequency

C
increases as square of frequency

D
decreases inversely with frequency

Solution

The inductive reactance $${ X }_{ l }=\omega L$$

Hence, $${ X }_{ l } \propto \omega $$

As frequency increases $$\rightarrow \omega $$
Therefore, inductive reactance increases with frequency.
Question 5
1 / -0

Directions For Questions

The above figure shows a cross-over network in a loud speaker system. One branch consists of a capacitor $$C$$ and a resistor $$R$$ in series $$($$the tweeter$$).$$ This branch is in parallel with a second branch $$($$The woofer$$)$$ that consists of an. inductor $$L$$ and a resistor $$R$$ in series. The same source voltage with angular frequency $$\omega ($$from an amplifier$$)$$ is applied across each parallel branch.

...view full instructions

The impedance of the tweeter and woofer branches are respectively

A
$$\displaystyle \sqrt{R^2+X^2_C} , \sqrt{R^2+X^2_L}$$

B
$$\displaystyle \sqrt{R^2+X^2_L} , \sqrt{R^2+X^2_C}$$

C
$$\displaystyle \sqrt{R^2+(X_L - X_C)^2}$$ each

D
$$\displaystyle \sqrt{\left(\frac{1}{R^2}+\left(\frac{1}{X_C}-\frac{1}{X_L}\right)^2 \right)^{-1}}$$ each

Solution

Impedance of tweeter$$ =\left | R + \frac{1}{jC\omega} \right | =\sqrt{R^2+X_C^2}$$
Impedance of woofer$$ =\left | R + jL\omega \right | =\sqrt{R^2+X_L^2}$$
Question 6
1 / -0

An inductor, a resistor and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance of the

A
inductor increases

B
resistor increases

C
capacitor increases

D
circuit increases

Solution

The reactance of inductor, $${X}_{L}=\omega L$$
The reactance of capacitor, $${X}_{C}=\cfrac{1}{\omega C}$$
where $$\omega=2\pi n$$ & $$n$$ is the frequency of A.C source.
Therefore, reactance of inductor increases.
Question 7
1 / -0

With increase in frequency of an AC supply, the impedence of an L-C-R series circuit

A
remains constant

B
increases

C
decreases

D
decreases at first, becomes minimum and then increases

Solution

We have the formula for Impedance

$$\\ Z=\sqrt { { R }^{ 2 }+{ ({ { X }_{ l } }-{ X }_{ C }) }^{ 2 } } \\ { X }_{ C }=\dfrac { 1 }{ \omega C } \\ { X }_{ l }=\omega L$$

And from the graph it can be easily seen that is $$Decreases$$ first and then $$Increases$$.
Question 8
1 / -0

The self inductance of a coil is 1/2 henry. At what frequency will its inductive reactance be 3140$$\Omega$$

A
$$100 Hz$$

B
$$10 Hz$$

C
$$1000 Hz$$

D
$$10000 Hz$$

Solution

We know that,

$${ X }_{ L }=\omega L$$

$$\omega =\dfrac { { X }_{ L } }{ L } $$

$$\omega = 6280$$

$$f=\dfrac { \omega }{ 2\pi } $$

$$f=1000$$ Hz.
Question 9
1 / -0

In a series combination of $$R,L$$ and $$C$$ to an A.C source at resonance. If $$R=20\ ohm$$, then impedence $$Z$$ of the combination is

A
$$20$$ ohm

B
Zero

C
$$1$$ ohm

D
$$400$$ ohm

Solution

At resonance, impedence $$Z=R$$
So, $$ Z= R = 20\ ohm$$
Question 10
1 / -0

In an $$AC$$ circuit, a resistance of $$R$$ ohm is connected in series with an inductance $$L$$. If phase angle between voltage and current be $${45}^{o}$$, the value of inductive reactance will be

A
$$R/4$$

B
$$R/2$$

C
$$R$$

D
$$cannot\ be\ found\ with\ given\ the\ data$$

Solution

$$\tan { \phi } =\cfrac { \omega L }{ R } =\cfrac { { X }_{ L } }{ R } $$

Given: $$\phi ={ 45 }^{ o }\quad \Rightarrow { X }_{ L }=R$$

User

Question Analysis

Correct -
Wrong -
Skipped -

My Perfomance

Score
-
out of -
Rank
-
out of -

Re-Attempt Weekly Quiz Competition

Alternating Current Test - 23

Result

Alternating Current Test - 23

Score

-

Rank

-

SHARING IS CARING

Question 1

effective resistance due to capacity

effective wattage

effective voltage

None of these

Solution

Question 2

$$\displaystyle \infty$$

zero

1 $$\Omega$$

2 $$\Omega$$

Solution

Question 3

$$C$$

$$L$$

$$R$$

$$L,\ C$$ and $$R$$

Solution

Question 4

decreases

increases directly with frequency

increases as square of frequency

decreases inversely with frequency

Solution

Question 5

$$\displaystyle \sqrt{R^2+X^2_C} , \sqrt{R^2+X^2_L}$$

$$\displaystyle \sqrt{R^2+X^2_L} , \sqrt{R^2+X^2_C}$$

$$\displaystyle \sqrt{R^2+(X_L - X_C)^2}$$ each

$$\displaystyle \sqrt{\left(\frac{1}{R^2}+\left(\frac{1}{X_C}-\frac{1}{X_L}\right)^2 \right)^{-1}}$$ each

Solution

Question 6

inductor increases

resistor increases

capacitor increases

circuit increases

Solution

Question 7

remains constant

increases

decreases

decreases at first, becomes minimum and then increases

Solution

Question 8

$$100 Hz$$

$$10 Hz$$

$$1000 Hz$$

$$10000 Hz$$

Solution

Question 9

$$20$$ ohm

Zero

$$1$$ ohm

$$400$$ ohm

Solution

Question 10

$$R/4$$

$$R/2$$

$$R$$

$$cannot\ be\ found\ with\ given\ the\ data$$

Solution

User

Question Analysis

My Perfomance

Score

-

Rank

-

Results Announcement on: coming Monday

Stay Tuned: We’ll update you on your result via email or SMS.