An electronic system, with closed loop current flow, and relative electrical potentials present across electrical components.

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Energy in a Solenoid?

Consider a circuit consisting of a battery, a resistor and a solenoid inductor. Then, the emf $\mathcal{E}$, is defined as: $$\mathcal{E} = L\frac{di}{dt} + iR$$ Multiplying both sides by ...
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44 views

Voltage Drop and Charge Flow

I am hoping someone can help me with understanding voltage drop and charge flow. Here is what I think I know. The voltage drop through a circuit must equal the voltage of the battery source, and ...
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43 views

Kirchoff Loop and current

The pic of the circuit/problem: I got the problem right, but i want to make sure my reasoning is correct for the current left of the 2.1 V battery. Its the same current as $I_1$ because the ...
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59 views

Wrong positioned Ampere-meter and Voltmeter [closed]

I'm dealing with a problem here and even that I'm trying to solve it i can't It says: In what figures the voltmeter and ampere-meter are wrong positioned? I think that all the the others are ...
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41 views

The effects of reversing the leads of an ammeter

I was playing around with a battery, an ammeter, and a light bulb. The ammeter originally read 1.99 A, but after reversing the leads going into and out of the ammeter the ammeter read -1.98A. I know ...
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39 views

Different phase in capacitively coupled RLC circuits

I was trying to work with some data for a lab report I'm writing about capacitively coupled RLC circuits. The setup is pretty simple and looks like that: Where $C^{'}$ is the coupling capacitance. ...
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44 views

Is R1 R2 and R3 parallel? [closed]

or R2 and R3 are parallel then they are in series with R1?
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32 views

Balanced three phase circuit Y-Y with neutral

Here is my equivalent balanced three phase circuit Y-Y with neutral: Rla + jXla is my line impedance by phase. L1 and L2 are my loads. The exercise is saying that L1 absorbs 180 W and 240 VAr, L2 ...
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57 views

Understanding Counter - EMF?

When an coil rotor is moving around a magnetic field there is -V induced to resist the input V. Let's take an example, a 12 V DC motor induces -10V, and the actual running voltage is 2V. If there ...
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85 views

Conversion of Moving coil galvanometer to ammeter

A galvanometer can be converted into an ammeter by connecting a low resistance (called shunt resistance) in parallel to the galvanometer. Firstly, why do we need to connect the resistance? If a ...
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46 views

Is there current flowing though a power source?

Would there be any current flowing though an ideal voltage source? I am asking this more specifically when you are analyzing a circuit and you are doing nodal analysis. I know i=v/r, but since the ...
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64 views

How to get a function for the voltage across a capacitor connected to an AC voltage source? [closed]

I am looking for the way of obtaining a solution for $V_{c}$ ,as a function of $t$ depending of $\omega$, of the following differential equation related to an electrical circuit involving a low-pass ...
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131 views

How do capacitors work?

Say you have a battery, with a wire connecting the negative and positive terminal. Initially, (the transient state) the electric field is not uniform and is perpendicular to the surface of the cross ...
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51 views

Electric shock from a frayed wire

Let's say it's a laptop charger not connected to a laptop, and it is frayed near the tip. I am guessing about 20Volts runs through that area. Now if a person touches a bit of plastic below the frayed ...
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93 views

How to find power factor value of parallel RL circuit knowing the power factor value for the series circuit with the same components

Because I know the value for the power factor for the series RL circuit I've tried to find the ratio between the series circuit power factor and the parallel circuit power factor, expressed in terms ...
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4answers
348 views

How electron movement produces current,instead of having a slow drift speed

Just need a clarification here, how the current is produced due to the movement of electrons, in an external circuit,having a very slow drift speed. Normally in a battery there is high potential ...
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2answers
306 views

Capacitors: why is the energy not stored in a magnetic field?

When a capacitor is charging, the rate of change $dE/dt$ of the electric field between the plates is non-zero, and from the Maxwell-Ampère equation this causes a circulating magnetic field. Now, ...
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27 views

Are magnetic hysteresis losses relevant to alternating currents flowing in a wire?

Say we have an AC in a magnetically lossy material, like iron. Because of iron's relatively high permeability, skin effect will be more pronounced than it is in say, copper, so this iron wire isn't so ...
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177 views

Surface charge in a wire?

The image above shows the distribution of the surface charge in a current carrying wire. The surface charges distributes themselves to make sure the field inside the wire is always perpendicular to ...
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266 views

Electric field in a wire?

The electric field in a wire is parallel to the wire's surface (it is always pointing "to the front"). If the electric field did not point in this direction, surface charges would build up and ...
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0answers
17 views

Resistor connections [duplicate]

I can't figure out what kind of connection it would be if i put resistors like this Can someone please explain how they are connected, like is R1 and R2 in series and R4 and R5 in series and then I ...
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68 views

Superposition theorem

Is superposition theorem applicable for circuits having semiconductor components like diodes, transistors, etc.?
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61 views

RLC circuit, turning off the voltage source

An RLC circuit (pictured above) is governed by two equations: $$ -iR=-L \frac{dj}{dt} = \frac{q}{C}+V(t) $$ $$\frac{dq}{dt}=i+j$$ q satisfies the equation: ...
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1answer
71 views

Voltage in a circuit?

The voltage of the battery signifies the difference in voltage between the positive and negative terminal What does this mean? The definition of voltage difference I'm familiar with is the ...
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27 views

Need to find the Vab of this circuit! [closed]

Find Vab in the circuit http://imgur.com/IqZ7Yis I uploaded a picture of the circuit. I tried adding 10 and 5 (top) because they appear to be in series. I also added 10 and 15 (bottom two) because ...
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137 views

How do I combine three resistors which are in parallel with each other?

For this circuit (a and b are connected by a battery), Will I be able to find the total resistance of the circuit by adding resistors that are in series and combining resistors that are in ...
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492 views

Why do electric motors draw current even when they are not moving?

After testing electric motors, I realized that these motors draw current even when they are not moving. I do feel that these motors are trying to move, but they are not really moving, in the end. ...
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198 views

Why does a fluorescent tube-lamp flicker before lighting up?

If you turn on a fluorescent tube-lamp, it flickers before lighting up. If you then turn it off and turn it back on after 2 seconds, this time it doesn't flicker but lights up straight away. If you ...
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563 views

Solving circuits using kirchhoff's laws and elimination method ( not any matrix method) [closed]

I need to solve this problem as part of my review in college physics. The task is to find the value of 5 branch currents using Kirchhoff's laws and elimination method (or maybe called elimination by ...
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2answers
132 views

Will I get a shock when I try to use my hair-dryer under water?

Occasionally people get killed in their bathtubs by having an electrical device such as a hair-dryer take the bath with them - in movies. It seems to be a common belief that this is realistic, even ...
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55 views

Where is the mistake in the following DC circuit analysis? [closed]

In the following circuit, I'd like to calculate the potential difference $V_{BA}$. One way is to solve the circuit, by calculating all the currents $I_1, I_2, I_3$. The system of equations is: ...
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122 views

How to calculate potential in circuit

In the following circuit (that has come up during a BJT DC analysis for what is worth), I'd like to calculate the potential at point B and point E. My notes say that $V_B = -10 + 0.7 = -9.3V$. ...
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70 views

How to convert RL Circuits? [closed]

How do we convert a parallel RL circuit into its equivalent series RL circuit ?
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185 views

Reducing Eddy current losses

Eddy currents are setup in any metallic block which is in the vicinity of changing magnetic fluxes. These primarily cause heat losses, and in certain cases causes damping of the relative motion ...
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145 views

Does AC current produce EM waves?

Does AC current in simple wires produce electromagnetic waves? AC current entails very rapid changes in polarity and therefore the electrons in the metal will feel rapidly changing forces which should ...
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62 views

Capacitors in parallel and dieletric [closed]

I'm trying to solve this problem: Two capacitors of capacitance $C_1=200pF$ and $C_2=1000pF$ are connected in parallel and loaded to a potential difference of $400V$. Subsequently the space ...
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1answer
126 views

Circuit with inductor and lightbulb when switch is turned off?

I want to know what happens with a lightbulb immediately after a switch is turned off. We're talking about a circuit with a battery (AC), an inductor, a lightbulb and a switch. I need to know it in ...
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1answer
183 views

Delta to Star/Y Conversions and vice versa in Electric Ciruits

We all know the basic rules for conversion of $"Delta"$ circuits to $"Star"$ circuits and vice versa. We also know that this is needed for simplification of circuits in complex cases. Can anyone ...
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99 views

How does the tester screwdriver work? [closed]

How does the tester screwdriver work? If I put the tester screwdriver inside a "phase" hole of an electric socket, it lits up. If I press my finger against the metal cap on top of the screwdriver. ...
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83 views

Microscopic model of RLC circuit equation by analogy to continuous medium mechanics

According to the analogy of mechanics and electricity, the 1-D system of damped oscillation is similar to the RLC circuit. The equation of damped oscillation is $$ f=m\frac{dv}{dt}+\gamma v+kx$$ ...
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83 views

Batteries connected in Parallel

"If we connect two batteries in parallel, the battery with higher voltage will discharge into the other one." What is the intuition behind this?
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33 views

Electrode potential

If I connect a zinc half cell (Left hand side) and a copper half cell (right hand side), I get an E cell value of 1.1V taken from the voltmeter. If I replace the voltmeter with a light bulb, I will ...
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2answers
249 views

Why is there no current flow when i connect two opposite terminals of two separate batteries

I don't understand this..maybe there is something wrong with my understanding of battery or electricity. I am learning about electricity more deeply this time. So please spare with me... So lets ...
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1answer
306 views

Electron flow and electric potential

In the physics tutorial topic on current electricty it defines the positive terminal as the high potential terminal and the negative as the low potential. When talking about positive test charges this ...
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3answers
686 views

Unbalanced wheatstone bridge

Suppose I have an unbalanced Wheatstone bridge (resistances $R_1, R_2, R_3, R_4, R_g$), to which I apply some voltage $V$. I need to find the voltage across the the galvanometer. Solving the system of ...
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49 views

Applying more current? [closed]

An electric motor draws 20 Amps, when at maximum load of x. Can that value of current be applied even if the load was ten times less than x from a certain power source?
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105 views

Traditional Kirchoff voltage law in AC circuit?

The traditional (not taking into account phasor addition or complex addition) application of Kirchoff Voltage law, i.e. $\Sigma\Delta V=0$ along a loop, does not work for AC circuits. We can sum the ...
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66 views

The origin of contact noise?

I was trying to measure the noise of a device with metal probes. I was not sure whether I should trust the results because I was told contact noise might contribute to some degree. I am a little ...
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2answers
219 views

What do we mean exactly by the positive/negative charges in cathode and anode?

In batteries, what exactly do we mean by negative and positive charges? My understanding is that the negative charge of the anode is basically an atom with an extra electron in the last orbital and a ...
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251 views

Resistors in series vs parallel

I understand that for resistors in series we need to add R for each resistor to get the equivalent resistance, where R is resistance. I also understand the mathematical manipulations that show that ...