# Quick questions for tomorrows E&M lab practical exam

• azsktbrdr
In summary, there are two things related to using oscilloscopes that the speaker is unsure about for a practical lab exam the next morning. The first is determining the frequency of a square wave between terminals B and C of a test box, which involves wiring it to one channel of the oscilloscope and adjusting the controls. The second is finding the maximum current in a circuit with a capacitor, inductor, 1000 ohm resistor, and function generator, which requires adjusting the frequency of the function generator and using the oscilloscope to measure the current. The speaker also has questions about the voltage scale of the function generator and where to place the leads of the oscilloscope. The summary suggests that the speaker has a good understanding
azsktbrdr
There are two things related to using oscilloscopes that I am a bit fuzzy on for a practical lab exam I will take tomorrow morning:

1) Use the oscilloscope to determine the frequency of the square wave between terminals B and C of the test box. ( We will press and hold down the button on this box to activate it).

I'm guessing the box has some kind of square wave function generator built in. So, it sounds to me like I wire this up to one channel of the oscilloscope and adjust the controls until I see the square wave on screen. Then, I take one full cycle of the square wave and count the divisions on screen. Then, multiply this by the time/div setting that is on the scope, and then calculate the frequency by 1/(time)? Does that sound correct?

The next problem:
2) First, before connecting the function generator to the circuit, set its output to a sine wave that is 8 volts peak to peak (peak to trough). Next construct the circuit shown (it's a circuit with a capacitor, inductor, 1000 ohm resistor, and the function generator all in series). Adjust the frequency of the function generator so that the current in the circuit is a maximum. Use the oscilloscope to measure the circuits maximum current at this frequency.

My questions for this problem are:
a) Should the function generator have an explicit voltage scale on it that I will be able to dial up the 8 volts peak to peak voltage? I don't remember the ones we've been using this semester having that capability.
b) To measure current, do I measure the amplitude and then multiply by the volts/div setting, then use ohms law to get the current? I = V/R I am really not sure about this one.
c) Just to make sure, I put the leads of the oscilloscope across the resistor, right?

Thanks very much for any help on this. Sorry to be so long-winded!

Tim

Last edited:
the voltage from the function generator may be ajusted using oscilloscope. There is one point- the input impedance of the oscilloscope should be set to high impedance (usually 1 MOhm)-but whether do you have this option or not depends on the oscilloscope.
Other sounds correct.

az,

1) That looks right.

2a) If not...well...won't you have something sitting there that can measure the peak to peak voltage of an AC signal? Hint: It has knobs and a screen!

2b) That's right. An oscilloscope always measures the voltage across its inputs (well at least that's almost always true, and it is here). So you have to find a way to get the current from that voltage reading. i = v/R is pretty easy.

2c) Well, if you put them across the resistor, the oscilloscope will show you the voltage across the resistor. That's what you want, right?

Go to bed; you'll do fine!

## 1. What topics will be covered on the E&M lab practical exam?

The E&M lab practical exam will cover topics such as electric and magnetic fields, circuits, capacitance, and electromagnetic waves. It will also include questions on relevant mathematical calculations and laboratory techniques.

## 2. How should I prepare for the E&M lab practical exam?

To prepare for the E&M lab practical exam, it is important to review all relevant lecture notes, textbook readings, and laboratory activities. It is also helpful to practice solving problems and performing laboratory procedures on your own or with a study group.

## 3. Will there be any hands-on components on the E&M lab practical exam?

Yes, the E&M lab practical exam may include hands-on components such as identifying and setting up laboratory equipment, performing calculations and measurements, and analyzing data. It is important to have a strong understanding of laboratory techniques and procedures for these components.

## 4. Are there any resources available to help me study for the E&M lab practical exam?

Yes, there are several resources available to help you study for the E&M lab practical exam. Your instructor may provide study guides or practice problems, and there are also online resources and textbooks that offer additional practice problems and explanations of key concepts.

## 5. Will the E&M lab practical exam be timed?

Yes, the E&M lab practical exam will be timed. It is important to manage your time carefully and budget enough time for each question or task. Be sure to read and follow all instructions carefully to ensure you complete the exam within the allotted time.

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