# Tagged Questions

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### Why is the current in an electric circuit constant?

Considering electrostatics, suppose we have two charges of equal value and opposite sign and we put electrons along the road between them: We know that the electrical force or field is different from ...
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### What is the difference between a circuit with a resistor and one without it in energy terms?

In Fundamentals of Physics (HRW), an equation is derived for the current in a circuit in terms of its emf and resistance by the 'Energy method'; that is, deriving emf=i.r and saying that the work done ...
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### Why the bulb does not glow in this configuration of batteries?

I connected a bulb to a battery positive terminals with positive and negative terminals with negative . It glows as it should but when i connect the positive terminal of the same bulb to the positive ...
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### Finding the current in a parallel circuit [closed]

Two resistors are joined as shown. The top resistor receives a current of 3 A. What is the current in the other resistor? What is the current that enters at junction A? I'm confused on how the two ...
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### How is voltage increased from a battery?

I have recently watched a video about a powerful Octa-copter that uses 30,000 Volt brushless motors to propell, the batteries however look quite small about a 19v laptop battery. How is the voltage ...
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Our home appliances are mostly resistive loads and the bill we pay for consuming power is actually real power. If we use more inductive loads at our home, will it just cause problems in power factor ...
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### What does raising voltage do?

If I raise the voltage of a wire from 0V to 1000V and then to 5000V, am I merely packing it with more and more electrons (with those electrons being trapped there until they find a path off the wire)? ...
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### Circuit breaker Trips during thunderstorm

The circuit breaker at the electrical mains trips at home when there is a thunderstorm outside. Why does this occur?
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### Potential difference (PD) and electromotive force (EMF) in terms of electrons?

I am trying to understand potential difference and electromotive force in terms of electrons. In the above 3 circuit diagrams the red shows (what I think to be) the distribution of electrons ...
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### Ambiguity on the notion of potential in electrical circuits?

As everybody else I have been taught elementary electrical circuits from secondary school to engineering level in analog electronics at university. Invariably, the notion of potential used to ...
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### Why does smashing a TV remote load its batteries?

Many times I had the same problem: my TV remote's batteries were too weak for it to operate, but then, when I shook the remote a bit and smashed it on my palm, somehow the remote regained its ability. ...
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### Why isn't resistance proportional to distance squared

Here we have a wire. At both ends there is an equal and opposite field caused by a chemical reaction. So, if we decrease or increase the distance between the two points, the strength of the field ...
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### Can we pass electricity through air?

Electricity: I was wondering, whether we can pass electricity through air over a distance of 100 meters or so as electricity means the flow of electrons and we have seen the discharge or movement of ...
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### How does AC current flow in an open circuit?

In common house hold wiring we have the hot lead, neutral and ground. If the hot lead in electrical wiring contacts earth ground (perhaps though a short circuit in the chassis of a device) then the ...
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### Simple Parallel Electric Circuit [closed]

Ammeter (A1) and voltmeter (V) in series have parallel connection to another ammeter (A2). Currents in A1 and A2 are respectively 0.2 and 1.7 amp. Voltmeter's voltage is 6 volts. How should I find ...
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### Why is parasitic capacitance in inductor said to be in parallel?

Internal resistance of inductance (or other devices) are said to be in series. But parasitic capacitance is said to be in parallel (in case of an inductor). Why is that so? What determines whether an ...
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### Could this open electric circuit work?

Two batteries are interfaced by a resistor. Parameters such as resistance can be set arbitrarily. Does it work?
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### How to measure area under the waveform (electric current)?

I have a current waveform from my circuit which goes up and down the x-axis. x-axis represents time and my y axis represents current. How should I calculate total area under the curve? Should I take ...
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### electric-circuits

Why can't you connect the + of a device to one battery and the - to another battery (and have it work)?
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### insufficient electrons in a conductor [duplicate]

We all know that if an electric field is applied across an isolated conductor, then charges are induced at either surface such that the net electric field inside becomes zero. Now if the applied ...
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### Understanding frequency of a signal

I'm trying to understand how can one transmit different signals on a same copper wire using different frequencies. How does the electrons actually interact with the frequency? And how does the ...
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### Origin of Overpotential in Electrochemical Cell

I'm well aware of the significance of overpotential and how it is defined to be the difference between the thermodynamically determined equilibrium potential and the experimental potential required to ...
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### Why are diodes able to amplify signals in groups, but not alone?

Single diodes can determine whether a signal passes or not (depending on the biased)(plus they can even rectify a signal), yet why does it take a combination of diodes(like a transistor) to amplify a ...
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### Why is emf equal to PD when circuit is “open”?

I understand that the set up of a battery consists of very good, but not ideal conductor, and therefore, some internal resistance exists. Also, I get that emf is the PD that would exist if the ...
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### What exactly is ''electric energy''?

If the two fundamental types of energy are kinetic and potential energy, is electric energy simply the kinetic energy of charge carriers? Also, is the statement "A cell converts chemical potential ...
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### Back $emf$ and power?

The formula relating current to back emf is $V-E=IR$ where $V$ is the source pd and $E$ is the back Emf. Thus it can be seen that as the back emf increases the current decreases. But what is the ...
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### Power wasted and power delivered?

If a power source is supplying a current I and a voltage V, that travels to its destination through resistors of restance R is the power delivered at the destination = $VI - RI^2$, where $(Pi=) VI$ is ...
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### Circuits and Power

"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest? a) V only b) V and W ...
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### How “earthing” electricity work?

I made a simple bulb-battery circuit and then I cut one of the wires and attached both ends to cemented floor, the bulb didn't glow, this means cemented floor is a ...
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### Finding the voltage of an inductor in a RL series circuit [closed]

Here is the solution: This assigned question is an odd one since it doesn't seem to have anything to do with phasors which is the chapter I am currently studying. I know that that the phase ...
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### Circuit analysis: Two nodes as one?

Can I treat these two nodes in the center as if there were only one node connecting these four components?
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### Does back emf occur in transformers?

Does back emf occur in transformers and if so does it reduce the efficiency of the transformer and can it be reduced?
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### How do the different types of energy apply to voltage in a circuit

I was just wondering what happens in a circuit in terms of different types of energy transformations. If you apply a voltage to a circuit then electrons start moving (very slowly). Since the electrons ...
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### The shape of the graph of the equation: $V= -r I + E$

I have recently collected data (for a school experiment) in order to measure the EMF and the internal resistance of a solar cell. The data complied with the equation: $V = -rI + E$, i.e. the voltage ...
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### The value of current and voltage in a circuit

The picture is just for example. I don't know why $i$ and $i_1$ have different directions and $i+i_1=0$ according to KCL. Also, the value of voltage at each element. I mean in why the $V$ of the end ...
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### electric current in parallel circuit [closed]

If I have a parallel circuit with two resistors ($R_1=48 \Omega$ and $R_2=16 \Omega$) - and $R_1$ has a $0.1 A$ current running through, is it possible to calculate the current through $R_2$ without ...
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### Current through two inductors after a long time

I'm having trouble with visualizing the following problem, which is asking me for the final, steady current in both inductors $L_{1}$ and $L_{2}$. I was thinking that after a long time, essentially ...
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### What happens if I throw a battery into water?

Today I have by accident thrown a AAA battery into a bucket of water. I fished it out of the water immediately (within 20 seconds or so) and nothing notable had happened and the battery is still full ...
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### How is the current flow perpendicular to the wire?

This answer gives a great explanation of how surface charge builds up to force the current to move perpendicular to the wire: http://physics.stackexchange.com/a/102936/41086 However, it fails to ...
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### Do batteries lose charge?

Say I have a charge of +q and -q on the positive and negative terminals of a battery. If I connect wires to each terminal, but don't connect the wires (essentially creating an open circuit), the ...
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### Why do both plates of a capacitor have the same charge?

How do we know that both plates of a capacitor have the same charge? You could argue conservation of charge, but I don't see how conservation of charge implies the charge on both plates is the same. ...
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### Is a capacitor in an open circuit charged?

Say I have a circuit consisting of a battery, a wire, an open switch, and a capacitor. The circuit is open since the switch is open. My book says that the capacitor will only be charged when the ...
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### Can resistance of wire be ignored

I was doing some physics homework involving direct current circuits and resistors in series, and I started to question the accuracy of the following property of resistors in series, namely that the ...
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### Why doesn't the electric field inside a wire in a circuit fall off with distance from the battery?

We studied electric fields due to point charges. The magnitude of these fields decreases with the square of the distance from the point charge. It seems to me that we could treat the positive ...
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### What is the current of a capacitor when the derivative of voltage is undefined?

This is from the textbook I am reading: I know this equation for capacitors: $$i=C\cdot \frac { dv }{ dt }$$ Here is my question: how can diagram (a) be allowed if the derivative of the voltage ...
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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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### 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 ...
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 ...