What is Dc: Definition and 1000 Discussions

I need to combine two DC voltages to scan and lock a laser. The scanning will be 0-100 V and the locking will be performed with a small correcting voltage, +/- 1 V. Both of these will be fed into a PZT driver. My advisor suggested using an opto isolator, however I am not sure how that would...

what type of DC motors that can be use for moving a heavy object ?

Homework Statement So, for a school project I have to make a resistance soldering iron. As far as I know, this requires a high current going through high resistance wire (such as stainless steel in my case). I need to make this run from a standard 120v 15A wall outlet. I have figured out so far...

HiI have a device comprising a dc motor connected to a body and connected to the motor are four rotor arms. As the rotor arms are rotated they pass a point on the body that applies load to the motor then rapidly de loads the motor. So that every quarter turn the motor is loaded and then de...

Hello, I'm a student currently doing my final year degree course in University College Sedaya International. I have given a project called as Microcontroller for DC motor control. The requirement of the project are :- 1). Type of Microcontroller = Microchip PIC16F876 2). DC motor 3). The...

Hello there Building DC motors has sort of become a hobby lately and I'm about to build the best version yet. However, I have a few questions when it comes to the brushes. I salvaged a couple of brushes from an old electric saw that my dad was throwing away but the resistance of those are much...

I found it very interesting to see that surface charge and the Poynting vector are being used to describe how a simple DC circuit actually works. Chabay and Sherwood have made an outstanding contribution to physics and engineering in their texts and papers. Of course others jump on the...

Hello. I was browsing online to answer the question to why RMS voltage is used as opposed to the average voltage (and by average I mean over half a period, roughly 0.64V_peak), and the explanation I found was that the RMS voltage would produce the same heat as equivalent DC through a resistor...

hey All, i have an old wall charger that is 120v AC input, 5V DC output @1 amp. when i put meter on output i get 5.19v dc. i need 5.00v dc. How can i get to 5.00v? I'm making a throttle position sensor test tool. manual is asking for 5.0v +,- 0.01 i plug power into wall, plug in TPS, use...

Hi, I can't figure out what is the physical reason behind the fact that, in DC RL circuit, for example, the series one, the current rises from zero (supposing state zero response), to its maximum value given by ohm's law. I've understood it mathematically but I can't physically explain why...

Hey PF, first time here, I have a problem I can't seem to solve! Any help is appreciated. I am using some DC motors with peristaltic pump heads to pump water (picture). I was having issues so I've broken my circuit down to the bare basics: 1) 12V regulated power supply 2) 12V motor 3)...

In synchronous ac machines, the field is usually on the rotor and the power winding on the stator, where it's easy to cool. The field draws a small current and needs only small brushes. In dc machines, the field is on the stator and the power winding on the rotor, where it's harder to cool...

I know there have been discussions on electromagnets, but I think my question here is specific and hopefully quite different. Using DC power only, what amount of pull might I expect from, let's say, 48v of decent lead acid battery or batteries? It occurs to me that one could use an ebike...

See picture, sorry that it's huge. V1 is a DC voltage and there is also an oscillating source of frequency omega. Let V be the voltage between the two resistors, I be the current exiting the cap, and I1 and I2 be the currents through the 2 resistors. Then we have: ## I_1 = (V - V_1) / R_1## , ##...

Homework Statement A group of students found an old DC electric motor in a box. They were looking for a small generator they could use to power their computer while they were out camping. Explain how they might do this with the motor they found. Homework EquationsThe Attempt at a Solution

how demonstrate the formula ? the relationship between Force and Voltage and Torque? how to prove that this formula? << e-mail address deleted by Mentor >>

Homework Statement A 180V separately excited DC motor has an armature resistance of 1.2ohm. When the note runs at 1200rpm,t he armature current is 10A. 1) Assuming that motor torque is constant at all speeds,d determine the mechanical torque and power developed in the motor. 2)Find the speed of...

Homework Statement A 250V shunt dc motor runs at 1000rpm while taking a current of 25 A. The motor has armature and field resistance as 0.2W and 250W respectively. Calculate (a) The speed when the load current is 50A. (b) Armature torque developed at both speeds. Homework Equations...

An 8.25 kW shunt DC motor is supplied with a terminal DC voltage of 300 V. The armature resistance of the motor Ra is 0.25 , and the field resistance Rf is 40 . The field winding consists of 1500 turns. An adjustable resistance Radj is connected in series to the field winding. Radj may be...

I live in the Virginia suburbs of Washington DC where the light pollution is such that it is impossible to ever see the Milky Way in the sky. Where is the closest place one could go to actually see the Milky Way and more stars?

Ac motor is 1.12 amp 3000 rpm 60 Hz 1/30 Hp sealed ball bearing. I want to use a 12 V dc motor. Any help would be greatly appreciated. Thank you.

Homework Statement Homework Equations I(t) = E/R [ 1 - e^-t/tau)] Vseries = Sum of voltages , Vparalel= V1=V2=V3... V=I*R The Attempt at a Solution

Hi I'm working on a project in school (or at home) about brushed DC motors. I have recently built a prototype myself but instead of using permanent magnets around the armature I'm using an electromagnet from another motor that died. I intend to build another motor using the same armature but...

I burned out my scavenged motor today and now I think I want to apply a little more thought to moving the project forward. I'm working on a centrifugal blower that can suck air through a charcoal filter so I can keep the air clean around my soldering area. I chose a tuna can for the housing...

I need guidance in the explanation of utilizing LED light bars for a different function then designed. I do stage production, sound and lights for concerts and would like to adapt these LED light bars to "blind" to crowd. My issue is that each light bar operates 12-30 Volts DC @ 300 Watts. In...

We all know that poynting vector could be used to calculate energy transferred in AC system, but I want to know if that theorem could also be applied to DC current? How to prove this? And how to prove energy transferred in AC system could be calculated via poynting vector?

1. Homework Statement A DC circuit is shown below. Note the ground (V=0) in the circuit 1- calculate the current through the 5Ω resistance. Use "+" sign for the current directed from right to left, and "-" sign if the current flows from left to right. 2- The sign of the potential at a is...

i am having a hard time understanding why do we place the brushes on the Magnetic neutral axis, the textbook simply says, because this is where the current reversal takes place, is the point where emf from different meet is the same as the point of current reversal?

In a RC circuit is voltage through a capacitor always consider negative no matter if you're going with or against the current when setting up a voltage equation?

Homework Statement When Voltage is oscillating (A/C), then in a simple circle with steady resistance, the current will be proportional to the voltage. When voltage increases, current will increase. And when voltage decreases, voltage will decrease. Is it also true that in a simple circuit...

I have recently learned that in order to vary torque output from a DC motor, I need to vary the input current. A project I am working on requires that I have a DC motor that will be backdriven while providing resistance to a lever. A max torque of about 10 lbft will be provided from the lever...

What HP of DC Motor is required to run a 2.5 KW DC Shunt Generator?

Homework Statement Find Vc(0) Homework Equations Nodal Eq , ohms law The Attempt at a Solution Can someone please check my work for Vc(0)? I'll appreciate it.

Homework Statement Using the superposition principle, determine the current i(t. 2. Homework Equations Zc = 1/jwC Zl = jwL V = I*R I = V/Z The Attempt at a Solution First, I converted inductor/capacitor to impedance: L = 1.5H -> jwL = j * 10 * 1.5 = 15j C = 10mf = 1/(jwC) =...

Homework Statement http://imgur.com/a/4YfkJ http://imgur.com/a/4YfkJ Homework Equations for t<0 I understand that Capacitor acts as an open circuit and goes away but why did the 90v and 6ohm resistor disappeared? is it because current doesn't go that way? and also in that KCL at node V1...

Homework Statement A battery of EMF 12.6 V and internal resistance 0.1 Ω is being charged from a DC source of EMF 24.0 V and internal resistance 1.0 Ω using the circuit shown in the figure below. V1 and V2 are high resistance voltmeters and R is a fixed resistor. (a) What is the polarity of...

well we have learned in school there are two types of current DC whichs direct and AC where the curve change dir alternately. so what if the the graph is not a sine curve or a cos curve. is there any other name for such types of current?

Hi, I'm going to pose my questions with a number of assumptions, so please pick me up on any that are wrong. I want to know the design choices behind electric trains historically and current, this will mostly require some context of induction motors and inverters. I don't know exactly how EMUs...

Homework Statement A DC milliammeter has a full-scale deflection of 10 mA and a resistance of 50 Ω. How would you adapt this to serve as a voltmeter with a full-scale deflection of 150 V? Comment on whether this voltmeter would be suitable for accurately measuring the potential difference...

I have a questions about AC and DC components being grounded to the same spot. I have a power supply box that takes in 120V AC and brings that into a transformer that converts it to 24V DC. On the way into the box the ground wire from the 120V AC is brought into a grounding terminal block and...

Hello, So I am in the process of designing a stair climbing electric handcart/dolley capable of lifting around 500 lbs {Washer/dryer or Refridgerator} up stairs. The idea was to use an electric motor, preferably DC for HighTorque Low Speed and for my powering options. The idea was to use...

So I'm working on a senior design project and was trying to use a DC motor to charge a battery. The point is to allow for quick use to charge a phone or a laptop in circumstances where you need a quick charge. We have lead-acid batteries connected in series and parallel to give us: 14,000mAh...

Homework Statement Hello I have a bit of a problem solving this A 20 kW, 500 V d.c. shunt wound motor draws a current of 45 A when running at full load with a speed of 600 rev min–1. On no load, the current drawn from the supply is 5 A. If the armature resistance is 0.3 Ω and the shunt field...

I'm doing a project where I need to hand power for dc motor (12V or 24V) and charge a super capacitor, and then use it to drive another 48V dc motor. I want to know which Super capacitor will be suitable? Please give suggestions for Super capacitor specifications for both 12V and 24V that will...

I am trying to figure out the best way to hook up two 12v DC peristaltic pumps to run as close to the same speed as possible. The manufacturing tests had the pumps running within 10ml per minute which is acceptable; when I hook the pumps up in series they are not even close. When hooked up in...

In the trapezium ABCD shown in the figure, AB = (x + 3) cm, DC = (2x − 3) cm and BE = EC. If the area of the trapezium is 15 cm2, find the length of DC to the nearest first decimal place. Take $\sqrt{19}$ = $4.36$ Have I done correctly, Okay first we know that area of a trapezium $15 =...

I have to say first that I found quite a similar question under https://www.physicsforums.com/threads/poynting-vector-dilemma.331375/ However those thread ended without real answer.There shall be the following simple setup: A battery, and quite at a distance a light bulb. They are connected by...

I have a question regarding this part from a book on electrical machinery (the author is highly reputed in India). While teaching the motor action at an elementary level, the torque developed in the motor is explained using the equation F=Bil. But this paragraph says that the torque developed is...

Hello everyone, So I am doing this EMC course and got to a section about cable shielding. It was suggested that the best way is to have a 360 connection to the chassis and to connect the ground of the PCB to the chassis as to provide a better return path for the current. It has been suggested...

Hi. Assume we have some circuit with resistance ##R##. In DC, the current ##I## linearly depends on the connected voltage ##V## by Ohm's law ##I=V/R## . In AC, we can independently connect any voltage and current to the system by using a transformer, provided we have a power source with...