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

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AC pass through capacitor

I am confused how AC pass through a capacitor? Can any one explain or have the vedio how AC pass through capacitor?
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1answer
177 views

Finding the voltage of the circuit?

Capacitor 3 in Figure (a) is a variable capacitor (its capacitance C3 can be varied). Figure (b) gives the electric potential V1 across capacitor 1 versus C3. The horizontal scale is set by C3s = 20 ...
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23 views

What exactly happens in an electric circuit?

After reading chapters on Electrostatics, I have been having lots of problems in understanding current electricity.I will be trying to tell what my problems are by telling what I already know.Please ...
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4answers
1k views

How can there be a current and an electric field in an idealized wire with no voltage drop?

In an ideal circuit, How can there be a current b/w points a & b, when there is no potential difference and thus no electric field between a & b? If there is no current, then where does ...
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2answers
32 views

Find the total current supplied to the circuit [on hold]

I tried but could not manage to find the correct equivalent resistance. Please tell the process. The answer is 3A
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1answer
32 views

Ohmic Heating in Wires

please could someone tell me why Ohmic losses are always referred to as $I^2 R$ losses? Here is my problem. If the power coming from a power station is fixed then you can either deliver this power as ...
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0answers
23 views

Find the equivalent capacitance [on hold]

On the plane capacitor below, the surface of the boards is $A$ and the distance between the boards is $d$, the dieletrics constants are $k_1$ and $k_2$. Find the capacitance of the capacitor in ...
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1answer
143 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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0answers
14 views

Relation of current with frequency and voltage [on hold]

I tried to solve a numerical problem but I got stuck and I think it very necessary I will drwa certain basic conclusions when I would found its solution. The question is: An incandescent lamp ...
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2answers
1k views

How do Zener diodes work?

I was going through some of the theory behind Zener diodes. I know what they're used to work at constant voltage, but I don't know how they work. Actually, I kind of get that too, I know that voltage ...
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0answers
26 views

Resistors in series [on hold]

Let $P$ be the equivalent power of three resistors of powers $P1$, $P2$, and $P3$, and let $I$ be the current flowing through the circuit. We know that voltage is $V = v1 +v2 + v3$ and: $$V = PI\\ ...
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18 views

Initial current, RC Circuit

The task goes like this: The voltage between the points A and B, in the circuit diagram below, is 100 V. What's the initial current through the resistor when we close the switch S? (Other components - ...
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2answers
12k views

Current in series resistors and voltage drop in parallel resistors

when we have resistors in series, the current through all the resistors is same and the voltage drop (or simply voltage) at each resistor is different. Question 1: it is fine that voltage drop ...
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1answer
896 views

Capacitor charging, work done by battery on changing polarity

A uncharged capacitor $C$ is connected to a battery with potential $V$. It becomes fully charged and has a charge $Q=CV$ stored on it. Now the polarity of the battery is reversed. The capacitor will ...
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4answers
144 views

Ohm's Law Question?

Since $V=IR$, if you were to have say a $5\:\mathrm{V}$ source connected directly to ground, no components in the circuit at all, you would need to add resistance for the current to flow? Or is there ...
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1answer
347 views

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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3answers
86 views

Why does the resistance halve when two resistors of equal resistance are in parallel? [closed]

This is the question and answer to a homework question and I do not understand why this is the case. What is the logic behind it?
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3answers
363 views

How do electrons actually move in a circuit?

Last year, we were taught about electricity, about how electrons move in a closed circuit. But as our teacher had not taught us about electric fields yet, she gave us a simplified model of motion of ...
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0answers
33 views

Why there is a difference in brightness of bulbs in series and parallel connection? [closed]

Yesterday I connected two bulbs of 40 watt/220 v and 60 watt/220 v in both series and parallel connections. I noticed that when i connected the bulbs in parallel the bulb having low power i.e of 40 ...
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4answers
80 views

Why is $R_2$ and $ R_3$ parallel with $R_1$ in this circuit?

I know that if $V_2$ wasn't there it would make sense if $R_2$ and $R_3$ were parallel with each other and in series with $R_1$. Why is it different in this case?
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1answer
39 views

Equivalent Resistance [duplicate]

I've never had problems in finding the $R_{eq}$ of a circuit, but in this case I don't really know how to do it:
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2answers
78 views

Optimal method for solving circuit

This problem seems quite simple, and I can easily find a way to solve it but the possibility of error in my method is extremely high. This is just a sub-task of a bigger task but this is the only part ...
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1answer
234 views

What does a negative Thevenin-equivalent resistance mean?

What is the physical meaning of negative value of "Thevenin" resistance? Sometimes in the calculations, a negative value of Thevenin resistance appears.
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7 views

Calculating Voltage Drop over a transistor [migrated]

I have the circuit below with a Bipolar NPN transistor I have a whole bunch of currents measured with the Amp Meters for various different resistances. How do I calculate the drop in voltage across ...
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1answer
139 views

Why the EMF of a battery doesn't depend on distance between the two electrodes?

I have read that resistance of a conductor is directly proportional to its length. So, the EMF of a conductor (electrolyte of battery) should increase with increase in length/distance between the ...
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1answer
55 views

Confusion with potential difference [closed]

I was trying to solve a hard problem involving a circuit like this: Find the reading on the voltmeter (red ones are resistors) I don't know how to think about potential difference across branches ...
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2answers
23 views

Calculating the energy supplied by a battery

If you wanted to calculate the energy supplied by a battery in time $t$ you would use $E=VIt$ where $I$ is the current through the battery. If the internal resistance is $r$ we could also use ...
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1answer
475 views

Non-conservative Electric Field

I was watching this video from Walter Lewin and while watching these two videos, I noticed there is a "contradiction" in what he is doing. All links direct you exactly to where he begins, so you don't ...
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1answer
23 views

Experiment for finding resistivity

I was reading an experiment to measure the resistivity of a wire. I understand everything except for why the variable resistor is connected to the side of the positive terminal of the battery. Since ...
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1answer
41 views

Calculating resistances in parallel

I was playing around with a question involving resistances in parallel. I realized that $n$ equal resistors (resistance $R$) in parallel have combined resistance $R/n$. I proved this using ...
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2answers
959 views

Why does current need a closed loop to flow?

My textbooks at the moment don't really explain the underlying theory of circuits. All I do is apply the rules I was taught when I solve these problems. I don't get why electrons need to have a closed ...
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2answers
48 views

Resistors in parallel: How do I make this rigorous? [closed]

In my revision guide it says "when two resistors are in parallel, the current has two paths it can flow through so there is less opposition to the current. This is why the combined resistance is less ...
3
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2answers
166 views

Why is there no induced electric field in the experiment (Faraday's Law)

Below are three circuit diagrams for each of Faraday's experiments that allowed Faraday to come up with Faraday's Law. In Griffiths' Introduction to Electrodynamics Griffiths states (on page 302 of ...
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1answer
13 views

Need help understanding appliance ratings

I keep coming across things like "A filament lamp rated 12 V, 1.0 A", or "a heating element rated 230V, 500W". I think the first one is saying that a 12V potential difference across it will make a ...
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10 views

Circuit providing output? [migrated]

What does it mean for a circuit to provide an output power of say 1000W? Is "circuit providing power" referring to the battery supplying energy to the external circuit, or is it referring to the power ...
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1answer
31 views

Difficulty understanding electricity concepts

In circuit diagrams what does it mean for energy to be used in going through a component? I usually see this when emf is being described: total energy supplied per coulomb by battery = total energy ...
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0answers
32 views

Is shaking a phone enough energy to charge a smartphone?

Is shaking a phone enough energy to charge a smartphone? For example I'd like to use some kind of power generator to charge smartphone's battery but I'm wondering if shaking (by hand, or motion when ...
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1answer
43 views

What happens here in this capacitor?

What happens when we earth the circuit as shown below, why should it matter? because potential at a point is relative? So if the earlier potential was $V_p$ at that point, it becomes $0$, so every ...
4
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1answer
36 views

Why an inductor parallel with a light bulb makes it flash as a key closes the circuit?

The title is a simplified form of my question. To be precise, I'm talking about the following circuit: The inductor has a resistanse equal to the resistor in the circuit. So, the question is that, ...
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2answers
45 views

What is the rigorous definition for current in a closed circuit?

I know that $I = \frac {dq} {dt}$, but I have trouble reconciling that derivative definition with my intuitive understanding of current. At an arbitrary point in wire, the current is obviously the ...
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0answers
8 views

Ambiguity with circuit symbols [migrated]

If I wanted to draw say a verical thermistor in a circuit diagram, it can look like any one of these four: Is there a convention for which one to pick, or are all of them valid in any situation ...
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2answers
36 views

Voltmeter in series with a component?

I always see voltmeters connected in parallel with a component, but what happens if you connect it in series? I think it's due to the high resistance of a voltmeter but I don't really see why this ...
2
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1answer
78 views

Circuit analysis (Kirchoff's laws) for multi terminal resistors

Consider a four terminal resistor as shown here There exists a matrix resistance equation of the form $V_i=R_{ij}I_j$ for some $4\times 4$ matrix $R$ for each such four terminal resistor. I want to ...
-3
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1answer
132 views

What would be the resistance of a wire, if it is stretched to double length? [closed]

If there is a wire of resistance $R$ and we stretch it such that it becomes 2 times longer, then what should be the new resistance of the wire?
8
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2answers
2k views

Tying knots in power cables to prevent power surge from lightning strikes

There are plenty of references to this claim on the internet that tying knots in power cables will prevent a piece of equipment e.g. television or computer from a power surge. How can this be ...
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3answers
4k views

Why the bulb glows brighter?

If the total current is divided into the branches in a parallel configuration and it is constant in series. How come the bulbs glow brighter when connected in parallel than when connected in series?
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3answers
56 views

Deriving ODE for voltage across capacitor-RC circuit [closed]

I need to derive an ODE for the voltage across the capacitor in a specific RC circuit. The circuit has 1 resistor, one input, one capacitor and a switch. So far I have $$\frac{dv}{dt} ...
1
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1answer
42 views

Typo in physics book (capacitors)

I'm currently working through an AP revision guide. The section on charging a capacitor outlines the following steps: When a capacitor is connected to a battery, a current flows in the circuit until ...
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1answer
22 views

How long can a cellphone battery(pictured) power a LED light that produces light equivalent to traditional 60W bulb(800 lumens)?

Assuming Energy Star rated LEDs which produces 100 lumens/watts. Battery rated as 9.88Wh. Power consumption by LED = 800 lumens/100lumens/watt = 8 Watts Does it mean that it will power circuit for ...
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1answer
22 views

Calculating half power frequency (frequency response)

I am having a doubt in calculating half power frequency for a given RLC AC circuit. I have attached images of two questions with their solutions. In the first question, the equation for ...