# Basic Electronics True or False Questions

1. Nov 17, 2011

### Femme_physics

I also needed to explain my answer... I hope it's all true. Can you tell me?

True or False
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The Effective Voltage in our houses (Israel) is 220 Volts, therefor the Max VOltage is 380 Volts.

FALSE

220$\sqrt[]{}2$ = 311

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The equivalent inductance between points AB in the following circuit is 90 mh.

http://img824.imageshack.us/img824/3699/coils.jpg [Broken]

FALSE, due to the calculations I made in the pic.

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The Duty Cycle of the final repeating signal is 66.66%.

http://img545.imageshack.us/img545/570/31464876.jpg [Broken]

True.

4/6 = 66.66%

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In a rectification circuit of an AC sinusoidal voltage with the help of a single diode we get the following wave form after rectification.

http://img197.imageshack.us/img197/8518/booep.jpg [Broken]

FALSE. You need 4 diodes for rectification such as in a Diode Bridge.

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The conductance of resistor R in the following circuit is 10 Mho.

FALSE

G = 1/100 = 0.01 Mho

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The Frequency of the following repeating signal is 6 Kilohertz.

http://img825.imageshack.us/img825/4918/xttx.jpg [Broken]

FALSE

f = 1/6
omega = 2pif = 2 x pi x 1/6 = 1.047 Hertz

Last edited by a moderator: May 5, 2017
2. Nov 17, 2011

### Staff: Mentor

Actually, you can use a single diode for rectification. You get what's called half-wave rectification (effectively chopping off the lower or upper half of the waveform, depending upon the diode's direction).

https://www.physicsforums.com/attachment.php?attachmentid=41007&stc=1&d=1321554469

The real problem here is fact that the shown resulting waveform does not resemble a sinewave nor any part of one.

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Last edited by a moderator: May 5, 2017
3. Nov 17, 2011

### willem2

It's perfectly possible to rectify an AC voltage with only a single diode, it just isn't very efficient. What do you think is the waveform that is produced, if you put an ac voltage source in series with a diode?

The frequency of a signal is 1/period. $2 \pi$ doesn't come in to it. I think you're confused with the angular frequency.

4. Nov 17, 2011

### Femme_physics

Last edited by a moderator: May 5, 2017
5. Nov 17, 2011

### technician

I agree with the other responses. You get this rectified voltage with 1 diode.
The frequency =1/T = 1/6x10^-3 =167Hz (the time scale is in milliseconds)
Cheers

6. Nov 17, 2011

### Femme_physics

Again, made a mistake The question is if I can rectify to THIS

http://img197.imageshack.us/img197/8518/booep.jpg [Broken]

With just one diode.

Last edited by a moderator: May 5, 2017
7. Nov 17, 2011

### technician

that is what you get with 4 diodes!!

8. Nov 17, 2011

### Femme_physics

Yes, that's what I meant. I just posted the wrong pic. There you go! Thanks.

So was I right about everything?

9. Nov 17, 2011

### technician

The frequency question is wrong because the time scale is in ms (millisecs) and the time for 1 cycle (T) is 6 x 10^-3s.
The frequency =1/6x10^-3

10. Nov 17, 2011

### Femme_physics

1/6x10^-3 = 166.6667 hertz

So the answer is 0.16 kilohertz and not 6 kilohertz. Therefor the answer is still "FALSE", correct?

11. Nov 17, 2011

### technician

that is it !!

12. Nov 17, 2011

### Femme_physics

You rock, technician! Thanks a bunch.

13. Nov 17, 2011

### technician

Thanks a lot.... can't wait to see what you come up with next!