An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In a electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.The SI unit of electric current is the ampere, or amp, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit Electric current is measured using a device called an ammeter.Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conductors, they cause Joule heating, which creates light in incandescent light bulbs. Time-varying currents emit electromagnetic waves, which are used in telecommunications to broadcast information.
Hi,
I am building a charger for my bicycle front and tail light that uses dynamo to charge them while cycling.
However, depending on my speed, current is fed differently to lights and they start to flicker. Therefore, I was wandering if there is a way to make a constant current source which...
Hey, so I'm just wondering what are the formulas needed to calculate the temperature of a wire after x amount of time as an electrical current is passed through it. I know how to solve for it... I just forgot the formulas.
Thanks
Homework Statement
I am confused what to do but I have to find the current through the battery:
Homework Equations
V=IR
The Attempt at a Solution
I decided to find the equivalent resistance and do V/R = I using the 14V, but I believe my Req is wrong. What is throwing me off is the...
Would lightning work in space? I think it would but you wouldn't be able to see it?
Let's say I have some sort of device that creates a lightning bolt, if I shot it at a watermelon in a vacuum or another target would it hit the target, or nothing happen because of the vacuum?
A work colleague of mine told me that if you have an AC voltage across a wire and the frequency is high enough, there would not be any current, because electrons don't have time to move from one atom from another. Is there any truth behind this?
Homework Statement
[/B]
Estimate the total harmonic distortion [THD] present in the current waveform using the formula:
Homework Equations
##THD\left(I\right)=\frac{1}{I1}\sqrt{\sum_{n=2}^\max\left(In\right)^2}\times 100\%##
The Attempt at a Solution
I have attached a worksheet for this. The...
Hello,
I'm wondering how you would go about drawing a Feynman diagram for a weak charged current scattering interaction of a positron and a proton. I have attached a diagram of what I have tried but it doesn't conserve lepton number (I think this is a problem, from what I gather...
Hello Experts,
I am a physics newbie with big ideas. I have a question.
I am thinking about how to produce a zero Resistance Current.
We know we can do this using super-conductors in sub zero temperature, but maybe there's another way.
My assumptions (which could be wrong):
1) Resistance in a...
Homework Statement
A single-turn wire loop produces a magnetic field of 41.2 μT at its center, and 5.15 nT on its axis, at 20.0 cm from the loop center.
Find loop raidus and current.
Homework Equations
F = qv x BThe Attempt at a Solution
I tried to use the above equation, but could not figure...
I'm having trouble understanding circuits, particularly voltage. So my question is more of a conceptual dilemma. Please correct my definitions and relations if it is incorrect. Voltage is the energy provided per charge, and this energy is converted to KE once the circuit is closed, or in other...
Is there a possibility that none of the current interpretations of QM are right?
Or is the current interpretations all that there will be on the table?
Homework Statement
Homework Equations
For a basic RC circuit during charging:
q = CV(1-e-t/RC)
i = V/R (e-t/RC)
The Attempt at a Solution
I can solve basic RC circuits but this is just out of my realm of understanding. I can also find the max charge of the capacitor. I'm not looking for...
The conservation of probability says:
$$\partial_t J^{0} + \partial{i}J^{i} = 0$$
Use the Schrodinger equation to obtain$$ J^{i} (\vec r)$$.
I have no idea where to start this kind of problem because the notation makes no sense to me. I would appreciate a hint or nudge in the correct direction.
Homework Statement
Find currents I1 and I2 in the following circuit:
Homework Equations
I know I have to use Kirchoff's loop rule but I am not sure of the current going through the 5 ohm and 8 ohm resistors, is it just I1 and I2 respectively? Also do I incorporate the large loop at the...
A long horizontal wire carries 22.0A of current due north. What is the net magnetic field 20.0 cm due west of the wire if the Earth's field there points downward, 40 degrees below the horizontal, and has magnitude 5.0 E-5 T?
My approach:
1. Drew north to the right and the wire lying flat, with...
Assume I have a parallel circuit of current sources with 5 current sources generating 1mA each. Therefore from both the terminals I will get 5mA total. Now if I add a battery to one of the terminals where current(i) will flow into my circuit. If i = 50mA, will I get 55mA current from another...
Hi everyone. I wanted to pose this question to those who are currently working as mathematicians (faculty members or postdocs, or those who finished their PhD and are working in industry), or current PhD students in math.
Did you double major in mathematics and physics in your undergraduate...
Okay, so in Griffith's introduction to electrodynamics, Griffith clearly defines surface current density as follows:
"when charge flows over a surface, we describe it by the surface current density, K. Consider a 'ribbon' of infinitesimal width dL running parallel to the current flow. If the...
There are two circuits, each consist of a cell and two bulbs, in one circuit they are in parallel, and in the other they are in series. What's the best way to remember which lamp has the greatest pd, current and resistance when one bulb is brighter than the other in the series and parallel circuit?
Homework Statement
A capacitor is made of two parallel plates of area A, separation d. It is being charged by an AC source. Show that the displacement current inside the capacitor is the same as the conduction current.
Homework Equations
Idisp = ε(dΦE/dt)
Q = CV
C = Aε/d
Xc = 1/(2πƒC)
Q(t)...
Homework Statement
The problem asks to find the Total Force on the Circuit Loop. I have a circuit loop with length 30.0 cm and width 10.0 cm with a current I2= 30.0 A that is flowing counter-clockwise. There is a wire that has the current I1=15.0 A flowing from left to right and is 7.50 cm from...
Homework Statement
Two coils P and Q are placed close to one another, as shown in the first figure attached. The current in coil P is now varied as shown in the second figure. Show the variation with time of the reading of the voltmeter connected to coil Q for time t = 0 to time t = t 2...
Homework Statement
See attached image for circuit diagram and givens.
The switch has been closed for a very long time.
a) What is the charge on the capacitor?
b) The switch is opened at t=0 s. What current initially flows?
Homework Equations
V = IR
Q=CV
I=I0e-t/(RC)
The Attempt at a Solution...
Homework Statement
The value of the line integral around the closed path in the figure is 1.79×10−5 Tm .
https://session.masteringphysics.com/problemAsset/1385538/4/32-22.jpg
There is I2 and I3 inside the closed loop.
I2 = 12 A
What is I3?
Homework Equations
Amphere's Law: B = Uo I(enclosed)...
Hi all,
I'm a current full-time employee in a calibration laboratory with a b.s. in applied physics. I see in my current position there is a ceiling for career opportunities and am looking to return to school for my masters. I feel that I would enjoy the clinical side of things, I consider...
Homework Statement
A resistor connected across an AC power supply has a current given by I=(1.35A)cos(300t) when connected to a power supply with emf 120 V rms.
Find the RMS current.
Homework Equations
IRMS=Imax/√2
The Attempt at a Solution
IRMS=Imax/√2
IRMS=0.477 A
INCORRECT
Not exactly sure...
< Mentor Note -- thread moved to HH from the technical forums, so no HH Template is shown >
Hi all,
I'm trying to find an expression for the current i(t) as a function of C and V_out (t) after t = 0. I have an answer but still not sure at all if its correct or not.
Here is my answer:
I know...
Homework Statement
An AC source was connected to a capacitor and an inductor (ignoring its ohmic resistance) in series. If the inductive reactance was equal to twice the capacitive reactance, and then the frequency duplicated, determine:
1. the relationship between the the current before and...
I'm looking for software that can simulate an ac circuit. After a quick google, I found several free online services (which I will try out). What I was wondering though is if anyone had some advice concerning my selection. A brief list of requirements: accurate simulation of different conductor...
Homework Statement
I’m trying to understand what voltage is. Getting confused. I've written my confusion as questions below and answered the questions.
(i) What is voltage?
(ii) What is voltage passing through a lightbulb? (iii) Is POTENTIAL just another...
Homework Statement
How to determine the current as a function of time that flows in 10 ohm resistor, 100 ohm resistor, and 15 microFarad capacitor?
Please help
Homework Equations
I = V/R
I_capacitor = I e^(-t/RC)
The Attempt at a Solution
I only know the equation V=IR and the capacitor...
Homework Statement
(see attached file)
Homework Equations
Kirchhoff's laws
The Attempt at a Solution
(see attached file) I only included the work for measurement 1 since measurement 2 follows from that.
I got both voltage values correct. However the paths of the current flow was incorrect...
Homework Statement
A rectangular loop of wire with sides H = 22 cm and W = 77 cm is located in a region containing a constant magnetic field B = 0.82 T that is aligned with the positive y-axis as shown. The loop carries current I = 334 mA. The plane of the loop is inclined at an angle θ = 30°...
I have decided that I want to pursue a career in physics and chemistry. It is very important to me that my career helps people. While I know that there are current testing and research being done for cures and treatments to numerous diseases, I don' think that biology is the field for me. Thus I...
Homework Statement
Given a circuit with a total of 3 sources , 2 Voltage sources and 2 Current sources and 4 resostors, Find the Cirrent I2 passing through the branch where R2 and V2 are. And I am asked to give the formula for the value of the voltage in the current source. Attached the...
Homework Statement
The question wants to know why th current should be small through a wire when using an ohmmeter.
Homework Equations
None
The Attempt at a Solution
I can't think of a solution, and looking online doesn't give any answer.
Hello, This is not a homework but I’m confused about current and voltage. My understanding is fragile and I need to reinforce it with your help. Below I’ve written what I think I know to be correct. Please correct me where required. This is high school physics.(i) Current is the...
Hello.
Let's take a transformer picture first.
The basic equation explaining how the transformer work is the equation of Faraday's law of induction.
\begin{array}{*{20}{c}}
{{V_P} = - {N_P}\frac{{d{{\rm{\Phi }}_B}}}{{dt}}\;\;\;\;\left( 1 \right).}\\
{{V_S} = - {N_S}\frac{{d{{\rm{\Phi...
Homework Statement
[/B]
Derive an expression for vc(t) in the circuit of Figure P4.13 and sketch vc(t) to scale versus. I attached a screen shot of the circuit for this problem.
time.
Homework Equations
V = IR
V = V0exp(-t/tau)
The Attempt at a Solution
[/B]
I am trying to find the...
Homework Statement
A Si diode is operated at the room temperature (27 °C). For a forward current of 1 mA, the voltage VD is found to be 0.9 V. If the VD is 1 V, the forward current = _____ mA. Given that nVT = 26 mV
The answer is 46.81
Homework Equations
Shockley diode equation?
The Attempt...
There is this debate in car audio forums of this question whether it is better to connect your amp ground to the frame of the car or the battery.. basically they haven't came to a conclusion so I was curious what you guys think...
Basically what I mean is that when you hook up an amp in the...
Homework Statement
finding the resistor and current which is following through the circuit[/B]Homework Equations
kirchhoff law
The Attempt at a Solution
almost as fig 1 ( 9v=3.458 mA and 12v=11.122 mA)
fig 2 (9v=1.472 mA and 12v=12.882 mA) i3=2.48 mA
Homework Statement
In the tuned circuit below, what will happen to the reading of the ammeter when:
a) source frequency increases. The voltage is constant
b) the capacitance increases. The voltage and source frequency are constant
c) The voltage increases. Source frequency is constant...
Homework Statement
The ammeter in the Wheatstone bridge of (Figure 1) measures zero current when the resistance Rvar of the variable resistor is set to 189 Ω .
What is the current IL through the left side of the bridge?
Homework Equations
Junction rule:
ILeft + IRight = I4
I4 + I2 = I1...
Hello,
I'm wondering if it is possible to calculate current the collector current of a phototransistor that is paired with an IR Led? I have an IR Led that is 13.6 cm away from the phototransistor and has a radiant intensity of between 65 mw/sr and 125 mw/sr. The phototransistor that I'm...
Homework Statement
[/B]
My question is regarding part C of the question.
Homework Equations
V = IR
V(t) = V(1-e^(-t/tau))
The Attempt at a Solution
My idea is to use Kirchoff's Voltage Law and find the voltage of the capacitor as a function of time, then since the voltage across capacitor is...