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All questions of Alternating Current for NEET Exam
Alternating current is represented by- a)
- b)
- c)
- d)
Correct answer is option 'A'. Can you explain this answer?
Alternating current is represented by
a)
b)
c)
d)
|
Divey Sethi answered |
Alternating current is an electric current which periodically reverses direction, as opposed to direct current which flows only in one direction. And it can be easily represented by the periodic function.
So, I = Io sin wt or I = lo cos wt.
So, I = Io sin wt or I = lo cos wt.
The average power dissipation in pure resistive circuit is:- a)
- b)
- c)
- d)
Correct answer is option 'D'. Can you explain this answer?
The average power dissipation in pure resistive circuit is:
a)
b)
c)
d)
|
|
Divey Sethi answered |
Power=IV
Where I=Vrms value of current=IV
And V=Vrms value of voltage=EV
Therefore, P=EVIV
Where I=Vrms value of current=IV
And V=Vrms value of voltage=EV
Therefore, P=EVIV
Find the instantaneous voltage for an a.c. supply of 200V and 75 hertz- a)E = 282.8 sin 50πt
- b)E = 282.8 sin 150πt
- c)E = 282.8 sin 75πt
- d)E = 282.8 sin 100πt
Correct answer is option 'B'. Can you explain this answer?
Find the instantaneous voltage for an a.c. supply of 200V and 75 hertz
a)
E = 282.8 sin 50πt
b)
E = 282.8 sin 150πt
c)
E = 282.8 sin 75πt
d)
E = 282.8 sin 100πt
|
Krishna Iyer answered |
Answer :- b
Solution :- f = 75hz
w=2πf
= 2 * π * 75
= 150π
E(max) = (2)^½ E(rms)
E(max) = 1.414 * 200
= 282.8V
E(ins) = E(max)sinwt
E(ins) = 282.8 sin 150πt
Which is more dangerous?- a)220 V a.c
- b)220 V d.c
- c)Both 220 V a.c. and 220 V d.c
- d)Both 220 V a.c. and 220 V d.c. are not dangerous
Correct answer is option 'A'. Can you explain this answer?
Which is more dangerous?
a)
220 V a.c
b)
220 V d.c
c)
Both 220 V a.c. and 220 V d.c
d)
Both 220 V a.c. and 220 V d.c. are not dangerous
|
Mihir Joshi answered |
The correct answer is option 'A', i.e., 220 V a.c.
Explanation:
Electricity can be transmitted in two forms - AC (alternating current) and DC (direct current). Both forms of electricity can be dangerous but the level of danger depends on various factors such as voltage, current, resistance, frequency, and duration of exposure.
Let's understand why 220 V a.c. is more dangerous than 220 V d.c.:
1. Effect on the human body:
- AC current alternates its direction of flow and causes muscle contractions and spasms, making it difficult for a person to let go of the source of electricity. This increases the risk of electrocution and can be fatal.
- DC current flows in one direction and causes muscle contractions and spasms but it is easier to let go of the source of electricity.
2. Frequency:
- AC current has a frequency of 50 or 60 Hz, which means it alternates its direction 50 or 60 times per second. This rapid change in direction makes it more dangerous and can affect the heart rhythm.
- DC current has a frequency of 0 Hz, which means it flows in one direction only and does not affect the heart rhythm.
3. Appliances and devices:
- Most household appliances and devices run on AC current, which means the chances of coming into contact with AC electricity are higher.
- DC current is mainly used in batteries, electronic devices, and some industrial applications.
Therefore, based on the above factors, it can be concluded that 220 V a.c. is more dangerous than 220 V d.c. However, it is important to note that both forms of electricity can be lethal and should be handled with caution. It is recommended to always turn off the power source before working on electrical equipment and to wear protective gear.
Explanation:
Electricity can be transmitted in two forms - AC (alternating current) and DC (direct current). Both forms of electricity can be dangerous but the level of danger depends on various factors such as voltage, current, resistance, frequency, and duration of exposure.
Let's understand why 220 V a.c. is more dangerous than 220 V d.c.:
1. Effect on the human body:
- AC current alternates its direction of flow and causes muscle contractions and spasms, making it difficult for a person to let go of the source of electricity. This increases the risk of electrocution and can be fatal.
- DC current flows in one direction and causes muscle contractions and spasms but it is easier to let go of the source of electricity.
2. Frequency:
- AC current has a frequency of 50 or 60 Hz, which means it alternates its direction 50 or 60 times per second. This rapid change in direction makes it more dangerous and can affect the heart rhythm.
- DC current has a frequency of 0 Hz, which means it flows in one direction only and does not affect the heart rhythm.
3. Appliances and devices:
- Most household appliances and devices run on AC current, which means the chances of coming into contact with AC electricity are higher.
- DC current is mainly used in batteries, electronic devices, and some industrial applications.
Therefore, based on the above factors, it can be concluded that 220 V a.c. is more dangerous than 220 V d.c. However, it is important to note that both forms of electricity can be lethal and should be handled with caution. It is recommended to always turn off the power source before working on electrical equipment and to wear protective gear.
The only component that dissipates energy in ac circuit is:- a)Capacitor
- b)Inductor
- c)Resistors
- d)None of these
Correct answer is option 'C'. Can you explain this answer?
The only component that dissipates energy in ac circuit is:
a)
Capacitor
b)
Inductor
c)
Resistors
d)
None of these
|
Hansa Sharma answered |
The only component that dissipates energy in ac circuit is the resistor because Pure Inductive and pure capacitive circuits have no power loss.
What is the relationship between Em and E0- a)Em=-0.537 E0
- b)Em=-0.737 E0
- c)Em=-0.637 E0
- d)Em=-0.707 E0
Correct answer is option 'C'. Can you explain this answer?
What is the relationship between Em and E0
a)
Em=-0.537 E0
b)
Em=-0.737 E0
c)
Em=-0.637 E0
d)
Em=-0.707 E0
|
Om Desai answered |
peak value Em=2E0/π
so 2/π value is 0.637
therefore,
Em=-0.637 E0
so 2/π value is 0.637
therefore,
Em=-0.637 E0
Given the instantaneous value of current from a.c. source is I = 8 sin 623t. Find the r.m.s value of current- a)5.656 A
- b)8 A
- c)2.848 A
- d)1.414 A
Correct answer is option 'A'. Can you explain this answer?
Given the instantaneous value of current from a.c. source is I = 8 sin 623t. Find the r.m.s value of current
a)
5.656 A
b)
8 A
c)
2.848 A
d)
1.414 A
|
|
Om Desai answered |
Compare the given eqn. with the standard from I=I0sinωt
I0=8, Irms=I0/√2=8/√2=5.656A
I0=8, Irms=I0/√2=8/√2=5.656A
If a capacitor of capacitance 9.2F has a voltage of 22.5V across it. Calculate the energy of the capacitor.- a)5062.5 J
- b) 2328.75 J
- c)50.625 J
- d)50625 J
Correct answer is option 'B'. Can you explain this answer?
If a capacitor of capacitance 9.2F has a voltage of 22.5V across it. Calculate the energy of the capacitor.
a)
5062.5 J
b)
2328.75 J
c)
50.625 J
d)
50625 J
|
Geetika Shah answered |
We know that,
ω=(1/2)CV2
After putting the values,
=(1/2)x9.2x22.5x22.5
=2328.75J
Hence option B is the answer.
ω=(1/2)CV2
After putting the values,
=(1/2)x9.2x22.5x22.5
=2328.75J
Hence option B is the answer.
Virtual value or effective value of a.c. is- a)-0.637I0
- b)-0.707I0
- c)0.637I0
- d)0.707I0
Correct answer is option 'D'. Can you explain this answer?
Virtual value or effective value of a.c. is
a)
-0.637I0
b)
-0.707I0
c)
0.637I0
d)
0.707I0
|
Preeti Iyer answered |
R.M.S. value or effective value or virtual value of Alternating current is given by
Irms = eo/√2 = 𝐼𝑝𝑒𝑎𝑘/√2 = 0.707 Io.
Irms = eo/√2 = 𝐼𝑝𝑒𝑎𝑘/√2 = 0.707 Io.
What is time constant- a)characteristic time with which current grows and decays
- b)the time current takes to reach the minimum value only
- c)time for the complete cycle
- d)the time current takes to reach the peak value only
Correct answer is option 'A'. Can you explain this answer?
What is time constant
a)
characteristic time with which current grows and decays
b)
the time current takes to reach the minimum value only
c)
time for the complete cycle
d)
the time current takes to reach the peak value only
|
Rohit Shah answered |
In physics and engineering, the time constant, usually denoted by the Greek letter τ (tau), is the parameter characterizing the response to a step input of a first-order, linear time-invariant (LTI) system. The time constant is the main characteristic unit of a first-order LTI system.
In the time domain, the usual choice to explore the time response is through the step response to a step input, or the impulse response to a Dirac delta function input. In the frequency domain (for example, looking at the Fourier transform of the step response, or using an input that is a simple sinusoidal function of time) the time constant also determines the bandwidth of a first-order time-invariant system, that is, the frequency at which the output signal power drops to half the value it has at low frequencies.
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