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.
Homework Statement
A certain commercial mass spectrometer is used to separate uranium ions of mass 3.92 multiplied by 10-25 kg and charge 3.20 multiplied by 10-19 C from related species. The ions are accelerated through a potential difference of 100 kV and then pass into a uniform magnetic...
An electric current in a wire occurs when...
A. electrons move in the wire as a result of getting pushed along from a neighboring electron.
B. electrons move in the wire as a result of the repelling force from the negative battery terminal and the attractive force from the positive battery...
<<Moderator note: Political statement removed.>>
To protect against a nuclear EMP (NEMP) usually a big metal box is used, which is electrically connected to earth, to discharge the electrical pulse.
Most houses in europe have a 3-grid electric system, L, Neutral (N) and Protective Earth (PE)...
Hello,
I've been googling about this topic and have read from a number of different books but I still haven't found an exact answer to my question.
It is known that the current is equal when the resistors are in a series. But the resistors per definition reduce current flow. If there are 2...
Hi,
I studied the Maxwell laws and the Biot Savart law and I found something I cannot answer.
If you have a finite wire carrying current (let say 5m long) and you want to determine the magnetic induction vector due to it at some point that has distance r from the wire, you have 2 options I...
OK, so my last post seemed meaningless.
Can anyone help with this, I understand some of you say current moves from the positive terminal of a battery to the negative terminal and some say the opposite.
Lets say it is positive to negative just for this question.
If I have a battery that the...
I measure sound (dB) from a speaker at 0cm and 100cm using a diaphragm microphone.
0cm-100dB, 100cm-30dB
diaphragm microphone cinsists of a diaphram, coil and a permanent magnet. the coil is attached to the diaphragm, when a sound wave hits the diaphragm it causes to move back and forth which...
I know that the right hand rule applies for induced currents, and the left hand rule is for motors, but why? It doesn't seem to connect with any other physics laws and is very counter-intuitive that the current will flow in one direction rather than the opposite direction if both are...
Homework Statement
Homework EquationsThe Attempt at a Solution
I am having a little doubt as to how to think of the moving electron as a current .
I am considering the moving electron as a very tiny (infinitesimal ) current element . It is as if when the electron is at A , there is a very...
For a Year 12 Assignment I have to do a seminar on how magnetic fields are involved with a certain topic. I chose nuclear fusion energy production and specifically the tokamak. I understand that a toroidal magnetic field is created when a current is sent through a solenoid wrapped in a torus...
Homework Statement
Homework EquationsThe Attempt at a Solution
The photoelectric current is directly proportional to the intensity of the light falling on it .
It will not depend on the focal length of the lens .
When the lens of half the diameter is used , intensity is halved . This...
Homework Statement
Homework EquationsThe Attempt at a Solution
The magnetic field lines due to the infinite wire will be clockwise .When P is the midpoint of the magnet , Magnetic field at the South Pole will have a component upwards and a component towards right .This means S will...
Trying to create an experiment that utilizes a motor driven shaft to measure the angular velocity of another shaft via eddy currents. We made a mock experiment that uses 8mm shafts, pillow bearings, and ceramic magnets from home depot, but don't see a torque on a non-ferrous metal attached to a...
Homework Statement
[IMG]http://[url=https://ibb.co/b3Emfo]https://preview.ibb.co/gLaEY8/20180527_055248.jpg[ A conducting bar slides down without friction on a pair of conducting rails separated by distance d. Connected to resistor R and there magnetic field B directed upward, perpendicular to...
Homework Statement
The capacitor is changed so that the largest possible current is supplied by the source.
Enter the value of the capacitive reactance when this change is made.
Give your answer in Ohms (Ω). A unit is not required with your answer.
Homework Equations
The circuit is powered by...
The kinetic energy of electrons in a conductor is roughly 9 orders of magnitude greater than the kinetic energy from the drift velocity of the electrons. It seems that the kinetic energy from the drift velocity is not enough to account for the heating, where does the heat energy come from?
Cheers
Homework Statement
In the circuit shown in the figure each capacitor
initially has a charge of
magnitude 3.60nC on its plates. After the switch S is closed, what will be the
current in the circuit at the instant that the capacitors
have lost 80.0% of their initial stored energy?
the shown 3...
Homework Statement
Homework EquationsThe Attempt at a Solution
First I will label a few points .
A is the point on the ring touching the rails , vertically below P .
B is the point on the ring touching the rails , vertically below Q .
T is the topmost point on the ring .
M is the bottommost...
Homework Statement
Homework EquationsThe Attempt at a Solution
For calculation sake I will consider R = 1Ω . Final answer will be in mA instead of A .
The middle two resistors 3R and 4R are in parallel , so I consider their equivalent resistance 12R/7 in the middle branch .
In the left...
Homework Statement
This is a multi choice question from last years aqa a level. We know a positive reading is produced on the scales indicating something is pushing down on the scales.
Please see the picture.
Homework Equations
We know current direction, not B field.
The Attempt at a...
Homework Statement
Homework Equations
Current cannot change suddenly through inductor unless input is impulse voltage source.
The Attempt at a Solution
since input is DC source we have i(0+) = i(0-) so we have di/dt at t = 0+ is 0.
Is it correct? Book has mentioned answer as B which is weird...
Hello,
I have a simple question regarding current flow through a common part of a circuit. I encountered this as I am reading "Code: The Hidden Langauge of Computer Hardware and Software" by Charles Petzold. The images I've attached display what I'm talking about. I'd like to know if there's a...
Hello.
Say I have a high powered device that draws continuous 18A. 3.7v
And I have one 3.7v 3500mah 18650 with a maximum continuous discharge of 10A, I know the battery will overheat and will most likely get damaged or shorten its life, or even catch fire.
But If I have another battery (same...
Homework Statement
In the circuit shown,the initial charge on the capacitor is Q0 = 200μC . If the switch is closed at t=0 , the capacitor starts discharging through the resistance R=4MΩ . What is the initial current (in μA) (i.e. at t=0) in the circuit?
Homework Equations
I = I0 e-t/τ
τ =...
Homework Statement
I'm asked to find the voltage, current, and resistance through each resistor in the given circuit.
Homework Equations
Req for parallel = 1/R1 + 1/R2 + ...
Req for series = R1 + R2 + ...
The Attempt at a Solution
First, I want to find the total resistance in the circuit...
Homework Statement
A long straight solenoid of cross-sectional area 400 cm^2 is wound with 10 turns of wire per centimeter, and the winding carry a current in the direction shown (downward). A small ring of radius 5.00 cm and resistance 0.300 ohms is placed at the center of the solenoid. If the...
Homework Statement
I was going through this PDF to review for my AP Physics C E&M exam: https://apcentral.collegeboard.org/...course=ap-physics-c-electricity-and-magnetism
I was also watching this video (which discusses the solutions):
I am stuck on part 2(b) (page 7 of the PDF, 17:18...
Homework Statement
Homework Equations
##J=\frac{I}{A}##
A=π r2
The Attempt at a Solution
Since I is constant and the diameter is doubled , A2 = π (##\frac{2D}{2}##)2
A2 = 4 A1
J2 = I/(4A1)
= J1 /4 → (E)
Is my answer correct ?
Say I have two parallel conductors that are both L long and d distance apart (center to center). I run AC power of frequency f and RMS voltage V through one conductor. That current will create a fluctuating magnetic field which will pass through the the other conductor and generate a voltage...
Homework Statement
AC production and relationships that determine movement and current flow direction from Flaming's left hand and right hand rule.
Homework EquationsThe Attempt at a Solution
Left hand rule for motors- right hand rule for generators
The thumb, index and midle fingers are all...
Homework Statement
Homework EquationsThe Attempt at a Solution
The two batteries are in series in both the left and right branch .This means the potential difference applied across the two middle resistors is 20 V .Hence the current flowing through them is 20/10= 2 A . This is indeed the...
I am wondering whether electrons have a net motion against an applied constant electric field in a conductor. Intuition tells me that "of course they should", but so far the math has shown me otherwise.
Here are my current thoughts:
1) I cannot rely on the obsolute Drude's model. What's more...
Homework Statement
Calculate the magnitudes and directions of the currents in each of the 3 resistors in the circuit above, if...
(a) ...both batteries have zero internal resistance.
(b) ...each battery has an internal resistance of 1.0 Ω.
Homework Equations
I1 = I2 + I3 (Node Law)The...
Homework Statement
The circuit above has five resistors. Calculate the current through each.
Homework Equations
I1 = I2 + I3 (Node Law)
∑Vi = 0 (Loop Law)
The Attempt at a Solution
I tried to equate the currents using the node law, with I3 = I1+I2+I4+I5
But I see a flaw here, because the...
Why don't wires in any circuit touch each other and get short circuited?
If two current carrying wires carry charges in same direction then from ampere's law,can't they touch each other due to attractive forces?
Homework Statement
provide a detailed review on how alternating current is produced and the relation that determins movement and current flow direction.
Homework EquationsThe Attempt at a Solution
I know the basics of how AC is produced- AC is produced from an alternater (type of generator)...
1. Homework Statement : Two identical uncharged capacitors A and B each of capacitance C and an inductor L are arranged as shown in the adjacent figure. At t=0, the switch S1 is closed while switch S2 remains open.At time t=to=√(LC)Π/2, switch S2 is closed and S1 is opened.
After switch S2 is...
Hi, maybe as you know ##\nabla. J = -\frac {\partial p} {\partial t}## where J is current density p is charge density.
But also we know current density flux outward the circuit is 0 because current density does not flow out of circuit an this actually volume integral of ##\nabla. J## is zero (...
Hi,
I was wondering about saturation current in the photoelectric effect. It is clear to me that for a sufficiently large accelerating potential all of the electrons are gathered by the collecting electrode. Since it is all of them, there cannot be more, and the current won't change if the...
1 Two cells are connected in parallel by joining the terminals together so that they both face in the same direction. One of the cells has emf 6.0 V and internal resistance 3.0 Ω, and the other cell has emf 4.0 V and internal resistance 2.0 Ω. An 8.0 Ω resistor is connected between the...
Homework Statement
Homework Equations
Kirchoff's Rule
The sum of all V = 0
The Attempt at a Solution
[/B]
I think I'm having a problem determining the current at r_2 and R_3. I had originally thought the currents at both resistors would be I_3, writing E_2 — r_2 I_3 — R_3 I_3 — I_1 R_1 = 0...
Hi, I've seen many videos of neodymium magnets sliding slowly down an inclined copper plate, or slowly down a copper tube - due to eddy current braking,but never the other way around. My question is; will a copper disc sliding down an inclined magnetic plate, or down a magnetic tube act in the...
Homework Statement
Homework EquationsThe Attempt at a Solution
I often do circuit. But still there is always stuff i don't get..
I was asked to find
1) I1 I2 I3 immidiately after S closed
2) I1 I2 I3 after sufficient of time
3) I1 I2 I3 immidiately after S opened
Just give me clue please...
Homework Statement
A coaxial cable consists of a core cylindrical wire and a coaxial cylindrical shell, as illustrated in the Figure below. Consider a cable made of copper, which has resistivity of
ρ=1.70×10−8Ω·m. Thecorewirehasaradiusof r =1.0mm. Theinnerradiusofthe 1
outer shell is r = 5.0...
Homework Statement
We bind two batteries with voltage 2V and 1.7V with inner resistance 0.2Ω and 0.1Ω in parallel series in such way that we bind each positive poles and negative poles together. What current runs trough the circle? What is the voltage between contact points of the batteries...
Homework Statement
Homework Equations
How will we calculate the current in primary coil?
The Attempt at a Solution
The current in the secondary coil will be 2 Amperes by I = V/R. So in the primary coil by using ratio proportion method, the current in the primary coil will be 5 Amperes. But...
Homework Statement
A wire with conductivity σ carries current I. The current is increasing at the rate dI/dt. Show that there is a displacement current in the wire equal to e0/σ⋅dI/dt
Homework Equations
Id = e0⋅dφ/dt
dφ/dt = dE/dt ⋅ A (This is usually true, I'm not sure if it's useful in...
When we talk about current and ohm’s law, do we pretend that current is continuous rather than discrete in the same way that we do with charge distributions?
A circuit contains a 7.5V d.c power supply and three resistors. The total resistance of the circuit is 30 ohms. Why will the largest current in the 18 ohm resistor? As far as I know is that the smallest current will be in 60 ohm resistor because it has the maximum resistance. Please explain...