Recent content by Leonid92

Hi all, I have a laptop Lenovo Thinkpad X1 Carbon 5th Gen (Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz 2.90 GHz, 8 GB RAM). It was bought with Windows 10 OS installed on SSD 512 GB (model of the disk is SSDPEKKF512G7L). Since the 1st running, the laptop was constantly heating and fan made much...

Thank you! After studying circuit theory, is it necessary to study antenna theory in order to develop RF coils for MRI?

Thank you for your answer! Could you please recommend a book where I can find the information about all parameters mentioned in your post and design of the neutralised inductor and coupling network in more detail?

Link to the Coil32 program: https://coil32.net/ Link to the formulas for calculation of inductance of one turn loop coil: https://coil32.net/one-turn-loop-coil.html

Thank you for your answer! ρ (Greek "rho") is characteristic resistance, or more correctly - characteristic impedance as zoki85 wrote. By placing resistor R1 in the scheme I tried to introduce characteristic resistance of LC circuit - it was a mistake. Because characteristic resistance...

Thanks a lot! I've just checked ρ value - it is approximately 20.735 Ohm ( √(L/C) ) as program Coil32 says. As I remember, Q = ωL/R. Q value obtained in the program is 792, ω = 2πf = 2π*10^8 (rad/s), L = 0.033*10^(-6) H. Thus: R = ωL/Q = 0.026 Ohm. On the other hand, R = ρ1*length/S, where ρ1...

Hi all, I'm trying to understand basics of radiofrequency (RF) coil development for magnetic resonance imaging (MRI). For example, the problem is to develop simple surface single-loop RF coil tuned to 100 MHz. In program Coil32, I set the following parameters: diameter of the loop D = 20 mm...

A schematic diagram is not given in the problem statement. I attached a sheme drawn on my own.

Given: U = 220 V f = 50 Hz r = 20 Ohm C = 100 μF Find: I Solution: 1) Xc = 1/(ω*C) = 1/(2*π*f*C) = 1/(2*π*50*10^-4) = 31.83 Ohm 2) R_eq - equivalent resistance R_eq = (r*Xc)/(r+Xc) = (20*31.83)/(20+31.83) = 12.28 Ohm 3) I = U/R_eq = 220/12.28 = 17.9 A True answer given in the textbook is 13 A...

Thank you for reply! When posting the thread, I made a mistake. Actually, H is not given. One should determine H using calculated B value and electrical steel magnetization curve.

1) B = Φ/S = (4.2*10^(-3) Wb)/(2.5*10^(-3) m^2) = 1.68 T 2) Using electrical steel magnetization curve given in the textbook: magnetic field strength H corresponding to magnetic flux density 1.68 T is equal to 6000 A/m. 3) L is a length of the middle magnetic line of the core (Fig. 2). L =...

In "Homework Equations" field, I wrote general equations for quadripole. I have doubt about the solution. True answer given in the electrical engineering textbook is P = 100 W. Here is my solution: 1) In scheme, I pointed currents and U(output) (Fig. 2). 2) U = A*U(output) + B*I2 I1 =...

I understood that there was typo in post #2 :) Thank you for your reply!

The true answer is given in problems section for specific chapter of the electrical engineering textbook (The chapter is called "Simple DC electrical circuits"). It is old textbook published in 1989, and there are some mistakes in it, but I thought that the answer given in this book for the...

Summary: How to find equivalent resistance of the electric circuit? I need to solve the following problem: Calculate equivalent resistance of the circuit (figure1), if all six resistances are the same: r1 = r2 = r3 = r4 = r5 = r6 = 100 Ohm. True answer: 66.6 Ohm. I tried to solve this...