Tagged Questions

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

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3
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1answer
596 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 ...
0
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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 ...
0
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1answer
139 views

Superposition theorem

Is superposition theorem applicable for circuits having semiconductor components like diodes, transistors, etc.?
3
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0answers
104 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: ...
3
votes
1answer
96 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 ...
0
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0answers
119 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 ...
0
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2answers
319 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 ...
6
votes
4answers
1k 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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3answers
1k 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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2answers
3k 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 ...
6
votes
2answers
283 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 ...
0
votes
1answer
64 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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2answers
227 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 $V_B = -10 + 0.7 = -9.3V$. ...
-1
votes
2answers
82 views

How to convert RL Circuits? [closed]

How do we convert a parallel RL circuit into its equivalent series RL circuit ?
4
votes
3answers
2k 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 ...
2
votes
2answers
416 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 ...
0
votes
1answer
74 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 ...
1
vote
1answer
237 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 ...
3
votes
1answer
891 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 ...
1
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0answers
132 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. ...
0
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0answers
169 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 $$ f=m\frac{dv}{dt}+\gamma v+kx$$ ...
0
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2answers
112 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?
0
votes
1answer
49 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 ...
3
votes
2answers
1k 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 ...
1
vote
1answer
2k 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 ...
1
vote
3answers
2k 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 ...
0
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1answer
50 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?
1
vote
1answer
189 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 ...
2
votes
0answers
80 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 ...
0
votes
2answers
644 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 ...
1
vote
3answers
392 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 ...
1
vote
4answers
267 views

Is voltage important when creating a magnetic field?

Would a DC circuit that has a high current and low voltage have a powerful magnetic field? I'm trying to create a powerful solenoid. In order to create a powerful magnetic field, I'm focusing more on ...
1
vote
3answers
1k views

Questions about voltage

For some reason, I feel like the concept of voltage is escaping my grasp. I've done much research on these forums and through texts, and come across answers that seem quite well thought out, but still ...
0
votes
2answers
104 views

Complex impedance triangle, why is there a complex part?

Why is the inductive reactance written as jωL? I know that multiplying by j rotates the inductive reactance on the j axis, but why do we do that? Why is it not on the same axis as the resistance?
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0answers
213 views

Variation of power factor with impedance in a series RLC circuit

I am solving this problem from a previous year question paper A series RLC circuit has resistance of 1k at resonant frequency and half power frequencies are 20kHz and 100kHz. Determine (i) The ...
3
votes
2answers
123 views

What is the area in Faraday's law if we have only a piece of metal moving in a magnetic field?

If a piece of metal of length $l$ is moving with a speed $v$ in a region where there is a uniform magnetic field $B$ perpendicular to it, there will be a potential difference across its terminals ...
1
vote
1answer
83 views

Capacitors in parallel and capacitors in series

How can I recognize clearly when I deal with capacitors in parallel or capacitors in series? Can follow a "rule" or a intuitive method? I have to do difficult exercises regarding system of capacitors ...
4
votes
2answers
132 views

Dimension of the space of solutions in an electric circuit

Consider an electric circuit with dc sources ( voltage and current) and resistors. Write down the equations. In the most general case, the solution of the system is not unique. The set of solutions ...
0
votes
1answer
142 views

Voltage and current in parallel circuit

I am having a bit of a tough time understanding the following: ...
0
votes
1answer
409 views

Power loss and Joule's law of heating

I really can't understand the power loss law. If we have a wire carrying a $15\:\mathrm{V}$ and $1\:\mathrm{ A}$ going into an inverter, giving $150\:\mathrm{V}$ and $0.1\:\mathrm{A}$, if we want to ...
2
votes
2answers
1k views

Measuring human resistance with a DMM

When I attach a Digital Multimeter (DMM) to read the resistance between my right and left hands, the resistance starts off high and reduces over time. It appears almost like "RC-type" behavior. Can ...
0
votes
3answers
206 views

Current without voltage?

Suppose you have a 120 volt, 20 amp circuit which only has a light bulb connected. When measuring the voltage going to the light bulb my meter reads 120 volts. The basics taught me that a circuit is ...
0
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0answers
37 views

Determine the current and voltage for every component in the following circuit [closed]

Determine the current and voltage for every component in the following series circuit What is the voltage and current through R1 and what is the voltage and current through C1? $V_1= 20\,V$ $R_1= ...
4
votes
2answers
1k views

Pn junction voltage drop?

This image from wikipedia, explains that there occurs a potential drop across a pn semiconductor junction, and an electric field confined to the depletion region. I already know the reason for the ...
2
votes
2answers
1k views

Can Kirchhoff laws be applied to any circuit?

Kirchhoff's loop/current rule is just law of conservation of energy and Kirchhoff's junction rule is just law of conservation of charge.So, I think that these can be applied to any circuits unlike ...
0
votes
1answer
129 views

Magnetic core, and a DC solenoid

A DC solenoid creates a magnetic field B. A highly permeability magnetic core is added to solenoid to increase B. Now, there is change in flux, due to the increase in magnetic field. What would be ...
3
votes
4answers
655 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 ...
3
votes
2answers
134 views

Is there a differential equation that can represent a circuit with an arbitrary voltage source connected acrorss an antenna?

An RLC circuit with a voltage source can be characterized by the differential equation: $$ LC\;\ddot{I}\left(t\right) + RC\; \dot{I}\left(t\right) + I\left(t\right)-C \;\dot{V}\left(t\right) = 0 $$ ...
0
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1answer
136 views

Voltmeter Question [closed]

I understand that a voltmeter is used for measuring potential electrical difference, but how exactly should said voltmeter be connected with the resistor in circuit?
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2answers
70 views

Calculating the power of a lightbulb [closed]

How do I calculate the power of a lightbulb? I have values but I don't know the equation to use.