# Can you help me prepare me for my E&M lab practical?

• rickyman
In summary, tomorrow's lab practical for E&M class involves using a multimeter to determine the contents of a "black box" with two electrical connections. The task is to find out what is inside without opening the box. This can be done by making measurements and identifying the box type, then using a strategy to determine the specific values for either a battery/resistor combo or a capacitor. Equipment provided includes a multimeter, computer with voltage-versus-time probe, miscellaneous resistors, wires and alligator clips, and a power supply.
rickyman
I have to perform a "lab practical" tomorrow for my E&M class and it involves using a multimeter to determine what is inside a "black box" - either a battery/resistor combo or a capacitor.

## Homework Statement

Taken from the lab practical write-up:

"You’ll be given a box with two electrical connections to the outside
world. One lead is marked plus and the other minus. Do not hook the positive
side of a power supply to the negative terminal on the box. Your task is to
briefly describe and apply a method for finding out what is inside without opening the
boxes.

1. Your box will be one of the above two types (they give two pictures - one for battery/resistor combo and one for capacitor). Briefly describe the strategy you
will use to find out which type you have. If you pick the right measurements,
only one simple one is required.
2. Make measurements and identify your box type.
3. Once you’ve identified your box type, briefly describe the strategy you will use to
do the following:
o If you have the battery and resistor box, determine the battery voltage
and value of the resistance. You will have only one multimeter, and it
must be used to measure voltage only.
o If you have the capacitor box, determine the value of the capacitance.
This will require measuring voltage versus time with the computer. A
separate sheet containing additional information that you may need is on
the front table.
4. Determine values for the data set pertaining to your box type.
Equipment for each setup:
• One multimeter.
• Computer with voltage-versus-time probe.
• Miscellaneous resistors.
• Wires and alligator clips.
• Power supply.

## Homework Equations

I know that if I determine that the box contains a capacitor I can find capacitance using RC=(t2-t1)/ln(V1/V2)

## The Attempt at a Solution

I am confused about how to approach this but I know that I will need to use the voltage measurement I take to determine what is inside. I just don't know how I will interpret the voltage measurement. I believe that the voltage measurement of the box if it contains a capacitor will steadily increase?

Any help is greatly appreciated.

Last edited:
I believe that if you connect the Battery-Resistor box with some dc supply, you will get a constant pd. only. On the other hand, an exponentially increasing potential differences, which attains a constant in the long run, will result if your box is the capacitor one.

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

The E&M lab practical will cover topics such as electric fields, electric potential, capacitors, electric circuits, and magnetic fields.

## 2. How can I best prepare for the E&M lab practical?

To prepare for the E&M lab practical, it is recommended to review your notes and textbook, practice solving problems, and attend any review sessions or office hours offered by your instructor.

## 3. Will there be any calculations or written questions on the E&M lab practical?

Yes, the E&M lab practical will likely include both calculations and written questions. It is important to understand the concepts and be able to apply them to different scenarios.

## 4. Can I bring a calculator to the E&M lab practical?

Yes, you may bring a calculator to the E&M lab practical. However, make sure it is a basic scientific calculator and not a graphing calculator, as the use of graphing calculators may not be allowed.

## 5. Are there any resources available to help me prepare for the E&M lab practical?

Yes, your instructor may provide study guides or practice problems to help you prepare for the E&M lab practical. Additionally, there are many online resources and textbooks available that cover similar topics and can serve as additional study materials.

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