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Questions tagged [electric-circuits]

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

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Change in electric capacitance and its factors

I've got some confusions regarding electric capacitance and I hope that you can help me see the picture more clear. Say that we have a capacitor with charge $Q$ and it's connected to a battery that ...
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26 views

How to compute electrical resistance from space varying resitivity?

We know that if resistivity is constant, the resistance can be computed from: $R = \rho L/A$. Similarly, if the material is non-uniform along its length, the resistivity can still be computed: $R = ...
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1answer
53 views

Electric Potential drop in wires

Electric potential is related to Electric Field by negative integral of Field with distance.If charges move away from the positive terminal (Assuming conventional flow) why is there no drop in ...
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1answer
103 views

If live & neutral alternates, why is neutral always $0V$? [duplicate]

So I've been confused on why the neutral is always at $0V$, I know that because it is earthed, but the concept that I know about AC Current that the Voltage keeps alternating ex(from $+240$ to $-240$)....
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2answers
71 views

Charging a battery

So we have a charger outputting V volts and $I$ Amperes and two rechargable batteries of the same capacity $Q$ coulombs but different emf's $V_1\&V_2$. Which battery would charge faster? ...
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38 views

Should not all electrical resistances be negative?

According to this image: Should not the resistance of the resistor be negative? Because the definition of resistance is $R = \frac {\Delta V}{I}$, and $I$ over here should be negative, considering ...
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1answer
62 views

Poynting's vector and its application to circuits

If I had a circuit as shown in the figure with the battery and the capacitor being covered completely, save for a passage for the conducting wire, by a hypothetical material that doesn't allow ...
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1answer
28 views

DC Battery Charging Question

I have a 7.4v LiIon that hold 1450ma. I have a variable DC bench power supply that I can crank up or down and adjust as needed. I want to quickly charge the battery and noticed if I adjust the ...
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1answer
47 views

Imprecision in experiments

When dealing with breadboards, and electronic circuits in general, in my case finding the total (equivalent) resistance using an ohmmeter, what are the factors that make the experimental value not ...
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2answers
453 views

Confusion on AC in LIVE & NEUTRAL WIRE

So if an AC current means the elctrons are alternating or changing direction in a given time, how does this apply to live & neutral wire, don't they flow in one direction only? Please answer it as ...
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2answers
48 views

Simple electronic circuit analysis [closed]

I have to find a substitute for this circuit. (The substitution is on the right) The arrows in one circle are perfect voltage sources. The arrows in two circles are perfect current sources. It ...
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1answer
37 views

Why is the current through this ammeter 0A?

I have the above circuit, and the current through the ammeter is 0A. But why is this the case? Is there any way I can easily show that the potential difference across that segment is 0V? Also, the ...
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1answer
114 views

Using Kirchhoff's laws to find currents [closed]

There are four resistors, R1=25Ω,R2=15Ω,R3=40Ω, R4=20Ω that are connected to an element 12V as shown in the figure. Find the current in each resistor. $I_1=I_2+I_3$, where $I_1$ is the current ...
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6answers
143 views

Right Hand Rule?

I'm trying to determine what the correct right hand rule is, but Google isn't helping. I've seen three different versions of Fleming's Right Hand Rule now, and I'm very confused. Here are three ...
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4answers
133 views

Why do we use the RMS but not the fourth root mean quad?

Why do we use the power of $2$? What is the relation between this and having the same heat energy in both AC and DC?
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2answers
56 views

Kirchoff's Second Law [closed]

I am failing to get a proper intuition on Kirchoff's law. If any closed loop has sum of pd and emf equal to 0, does that mean that this picture's loop also follows the same? I am not able to draw a ...
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1answer
36 views

Sinewave in DC powersupply

today in our physics class we talked about the hall-effect. Therefore we have used a Lab Quest with a sensor to measured the magnetic flux induced by a coil. While adjusting the current to gather some ...
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1answer
27 views

What does ground in low voltage electronic circuits mean?

I have been confused a lot by the word "Ground". The ground that I've usually heard about is connecting a wire of appliances with the rod buried under earth but what does the word Ground mean when it ...
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1answer
46 views

Effect of an open circuit in one branch on other branches of a parallel circuit

I'm looking at current readings from each branch in a fairly simple parallel circuit, and I'm trying to make sure that I am correctly diagnosing the problem based on the trends that I'm seeing in the ...
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2answers
62 views

How could a bulb light up if aĺl the voltage is lost in the resistor?

I recently came up with this slight confusion about voltage loss in resistors/resistance. So for example My circuit has a 12V battery, a 2 Ohms resistor and a Bulb. If we use the V=I.R formula then a ...
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2answers
57 views

Velocity factor in coax cables

I mainly see the term "velocity factor" used when referring to the velocity of propagation of an electromagnetic wave front in coax cables. This velocity seems strongly dependent on the properties of ...
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1answer
36 views

How do we generalise a specialised case in physics?

I have come across this sort of thing a lot of times in my textbook. I give the examples below- Eg.1- In the case of a capacitor connected across an alternating current generator, we find $V_c=...
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1answer
32 views

The effect of the resistance of coils on DC motor

I have some doubts on how the resistance of coil affects the efficiency of a DC motor. I assume there are two DC motors operating under the same supplied voltage, and the resistance of the coil $R_1$ ...
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1answer
38 views

The formula to calculate the life of a battery in a given circuit is calculated by the formula: E.E=V.I.t

The formula to calculate the life of a battery in a given circuit is calculated by the formula: E.E=V.I.t, using this formula, how can the time the battery will work be compared in different circuits?(...
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2answers
61 views

A battery generates current according to the resistances within a circuit(V=IR)

A battery generates current according to the resistances within a circuit(V=IR).The charged particles enter and exit the source with the same magnitude, however, since we have said that the current is ...
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4answers
48 views

Is there a physical explanation for why increasing a capacitor's capacitance and the circuit's resistance decrease the capacitor's rate of discharge?

The voltage across a capacitor as a function of time is given by: V=Vi(e-t/RC) Therefore, increasing the resistance and capacitance increases the time it takes for the initial voltage to drop to e.g....
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2answers
196 views

What is the difference between a galvanometer, an ammeter and a voltmeter?

I'm looking for basic differences b/w the three with respect to nature of the circuit as well i.e either it is connected in parallel or series, and also the reason as to why they're connected the way ...
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3answers
151 views

Can Kirchhoff's Voltage Law be applied here?

First, consider a simple circuit comprising of an ideal battery of EMF: E and a single resistor of resistance R. Imagine that the switch is opened in the circuit. In the battery, some internal ...
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2answers
408 views

Why doesn't using more appliances at home decrease the electricity bill? [closed]

I know that at home the electric circuits are parallel, and this explains why if one appliance (eg bulb) fails, everything else continues to work, but if more devices are added in parallel to each ...
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2answers
48 views

circuit analysis [closed]

I have been struggling with this circuit below since my teacher asked a question about it. The question is: -Is there any current flowing in the wire in the middle? The answer is yes. I tried to ...
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3answers
84 views

Do power supplies have to heat up?

Is there a fundamental reason why a power supply, say, from 120v AC to 12v DC, has to lose some power to heat dissipation? I am not asking why current engineering solutions do; I'm aware that ...
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1answer
38 views

Current generation

No matter the arrangement of resistors in a circuit, a battery will still produce a current as if it were connected to an imaginary combination of the individual resistors within the circuit? Can ...
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2answers
39 views

Capacitors phenomena

I wanted to ask one simple question: when there is a uncharged capacitor directly connected to a battery with any resistance in between, does current flow in the circuit, or does it only flow until ...
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1answer
27 views

Physics of ballasting a transformer, does ballast have an equation?

Does ballast have units? How much ballast do you need e.g. for limiting the current to a reasonable level for the plasma from an Mot? I got a Transformer out of the microwave and the internet ...
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4answers
95 views

Is the vacuum permittivity a result of defining other units first?

From Coulomb's law $$F=\frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}$$ If instead we defined the charge of a coulomb to be $\sqrt{\epsilon_0}$ times it is now, the force would be exactly the ...
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3answers
65 views

How to intuitively think (or get a 'feel' of L-R circuit)?

I've recently learned a little about R-L series circuit. Consider a simple L-R circuit, as shown in the given image- - (https://i.stack.imgur.com/ovfbQ.jpg) An inductor L is connected in series ...
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1answer
18 views

Reconciling two views of Matthiessen's rule for electron mobility

My understanding of Matthiessen's rule is that when electron conduction in a solid is inhibited by more than one mechanism, that the overall resistivity $\rho$ is formed as if these resistance source ...
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2answers
77 views

when the current flow through a resistor, what does it lose?

We all know that in a series circuit, the current is the same for all of the elements. But when the current flow through a resistor, what does it lose? The current is the same because it doesn't ...
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3answers
108 views

Current in series circuits [duplicate]

Current is calculated according to the resistances in a circuit. Then, why is the current same everywhere in a series circuit? Shouldn't a greater current pass through the smaller resistance? I am ...
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2answers
91 views

Path Of Current In A Wire

Why does current follow the path of least resistance? Will all current pass through a wire with $0$ resistance in a junction leaving other resistive wires with no current?
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3answers
116 views

This question was on my physics test (about basic DC circuits) [closed]

So in the following question: Because the wire has a resistance of near 0, is there no current going through the resistor with the arrow pointing at it. I understand that normally both resistors in ...
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1answer
42 views

How can only 2 phases of a 3 phase power system be used to power a load?

When looking at 2 of the 3 phases on a graph, there's a point where they're both positive or both negative. How does one of the phases act as a return path?
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1answer
28 views

Magnetic Dipole from 'Current' in LC Circuit

We can work out the 'current' in an LC (series) circuit by creating and solving an ODE: $$I\frac{1}{LC}+\ddot{I}=0$$ This provides us with a sinusoidal resonant response to any initial current. ...
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2answers
59 views

Voltage and current for travel kettle

I used a 500 watt travel kettle in France last year and it tripped the electrics in my hotel room so I stopped using it. I assumed the current was too high, even though its wattage rating wasn't that ...
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1answer
51 views

Is there a constant value of the time constant RC [closed]

Would it be correct to say that there is a definite, finite value of time constant in a Resistor- Capacitor circuit, i.e is there a constant value for RC ( where R is resistance and C is capacitance)
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1answer
45 views

Why can you assume the current remains the same after changing resistance?

In my physics textbook there is a question about a circuit: In question b) We find out the current in the circuit is 0.003A. This is before the voltmeter is added. In question c) a voltmeter is ...
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2answers
42 views

Relation between charge and potential difference in transient and steady states

I'm must be missing something again but isn't there some contradiction in 2 statements below ? Edit: I've rewrote the post and added images for clarification. On one hand, PD depends on amount/...
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3answers
161 views

Why can't we add the emf of two batteries in a parallel circuit?

My teacher told me that two batteries' emf cannot be added in a parallel circuit but can be added in a series circuit. However I can't seem to fully grasp why and I think there may be some loopholes ...
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1answer
41 views

What is the ratio of the turns in the transformer when it is impedance-matching?

I study physics on my own. There is a question in my textbook: A transformer may be used to provide maximum power transfer between two AC circuits that have diffirent impedances $Z_{1}$ and $Z_{2}...
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3answers
59 views

How LC oscillator is used for generating signals?

I have been trying to understand some practical applications of LC oscialltors and I dont seem to find much information available on net. One consistent application that I see is "LC circuits are used ...