All Questions
Tagged with electricity electric-current
791
questions
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Does a higher voltage always mean a higher electric field strength?
In a step-up transformer, the output voltage is higher than the input voltage, while the output current is lower than the input current. Basically, since P = VI is conserved, the current has to ...
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EMF of source depends on the charge and the path then what do we mean when we say EMF of a source is $\epsilon$?
EMF of an EMF source (a battery for example) is defined as the work done by the non-conservative force(s) on charged particles as it passes through the terminals of the source divided by the charge of ...
- 480
2
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2
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329
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We know that $R={\rho l/A}$ but how do you define L and A, Area of cross section?
How do we define area of cross section of a conductor for resistance of a metal piece.
When you a wire which is generally cylindrical you have a length of it. Its area of cross section is a circle ...
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2
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596
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Electric potential and kinetic energy in any flowing charge
We just started with electricity in school(grade 10) and I have some confusions regarding electric potential.
According to my book,
The potential at a point is defined as the amount of work done per ...
- 1,168
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555
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Electric current - In a simple DC circuit does the return wire carry the same amount of current back to the battery?
A = Amperes as symbol.
Take a simple DC current that has a battery, a light bulb, and to copper conductors. If the current coming out of the negative terminal of the battery.
let's say 1 amp, but the ...
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96
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Principle of working of a transformer [closed]
What is the principle of working of transformers?
Magnetic effects of current
Mutual induction
Self induction
Chemical effects of current
I know that Mutual induction is the right answer, but isn't ...
user319029
0
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2
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48
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Is my understanding of resistance varying with length correct?
Let us consider a copper wire of mass $1\ \mathrm{kg}$ and length $1\ \mathrm{m}$. Let the temperature & cross-sectional area be constant.
Case 1 :
If I cut the wire with a scissor, and make it ...
- 1,018
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63
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Applying KVL to batteries with different EMF in parallel
Consider the circuit diagram below-
Two batteries of different voltages are placed in
parallel, however as I was told that KVL is applicable to all loops if there is no varying magnetic fields, ...
-1
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2
answers
196
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Heating effect of electric current
I know that
$$H=I² rt$$
I also know it's mathematical derivation , but I can't understand that how the heat is proportional to current squared what must be the logic behind it. I can prove it ...
- 395
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2
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236
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How do I find the current density vector in an electromagnet that has a time-varying current?
I know that the current $I$ is a scalar quantity, and to calculate current density $J$ , the cross sectional area $A$ is needed, to give us $J = IA$ .
$J$ also has other relations involving ...
user320191
20
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4
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Are the "bird sitting on a live wire" answers wrong?
Long ago, my high school teacher wrote the popular question on board,
"Why doesn't a bird sitting on a live wire get electrocuted?"
He gave us four options (I don't remember all of them) ...
- 1,441
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4
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812
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Why is current = 0 in open circuit?
This is an open circuit. Now, a chemical reaction happens in the cell which makes the current to flow in the wire. Then, the current has no other place to go, so it just gets grounded. It is similar ...
- 294
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1
answer
73
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Running electrolysis on inside surface of a tube
I use electrolysis for rust removal and electroplating. I notice that when one of the electrodes is a closed tube or has other topological holes with a sufficiently large height:diameter ratio, the ...
- 1,004
21
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8
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13k
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Why do we reduce only current to prevent power loss? Why not voltage?
In power transmission lines current is kept low and voltage is kept high to reduce the power loss. This is because $P = I^{2}R$ and $P = VI$. In order to reduce power loss we have to reduce $I$ since $...
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Potential difference between two hollow spheres and amount of current flow
If two Hollow Spheres with radius $r_1$ and $r_2$ have charge $q_1$ and $-q_2$ in them respectively(charges are evenly distributed in the surfaces).The spheres are separated by a distance d .Now We ...
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6
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2k
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Electric current definition
I'm trying to understand electric current. Some resources say that it is the flow of charge, and other resources say that it is the quantity of charge that passes through a cross-sectional area over a ...
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4
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Current vs voltage in high voltage transmission lines
I know this question has been answered many times, but sadly I'm still not quite sure I get it.
Here's my interpretation, please correct me at any point:
We have some source. There's various ways to ...
- 135
1
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1
answer
67
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Second-order equation for the resistance of a filament lamp
I am trying to determine the initial resistance $ R_0 $ of a tungsten filament in a filament lamp, by quadratic approximation of the resistance
$R(T) = R_0[1 + \alpha*T + \beta*T^2]$
but I can't find ...
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1
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75
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Relative Amplitude: Current at full brightness [closed]
What is the relative amplitude of the flow in the filament of a miniature lamp the instant power is applied in comparison with the current at full brightness?
a. High
b. Low
c. The current is the same ...
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3
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If the earth is negatively charged why is lightning striking it?
So, as far as I know, the Earth is negatively charged, and there are such things as lightning strikes which travel from clouds to the Earth- that would mean the clouds in a thunderstorm are positively ...
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2
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2k
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Will solenoid expansion take place when current is flowing though it?
I came across this when doing my revision exam paper and had this doubt. I wanted to ask whether a solenoid will expand radially outwards when current flows through it.
(The actual question was ...
- 79
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1
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24
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In applications where heating is not the required from of energy, current is to be kept low as per Joules law. What energy is considered useful?
As per this paragraph from Wikipedia
"Joule heating is referred to as ohmic heating or resistive heating because of its relationship to Ohm's Law. It forms the basis for the large number of ...
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43
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Can current due to potential difference of earth's crust and ionosphere charge objects?
A man fixes outside his house one evening a two metre high insulating slab carrying on its top a large aluminium sheet of area $m^2$ . Will he get an electric shock if he touches the metal sheet next ...
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1
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346
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How Does Voltmeter Actually Work?
I've tried to find a specific answer to my question, but couldn't.
My question is why Voltmeter Shows Zero Volts, when we connect the leads not across a resistor (or any other component) but side by ...
1
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2
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39
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Resistance And Electric Power
In a practice problem A motor rated at 20 A with a voltage of 115V exerts a force of 4900 N over a distance of 10 m in 30 s. Using the formulas $P=VI$ and $P=\frac{Fs}{t}$, we can see that the motor ...
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382
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Why is the brightness of a light bulb dependant on power?
If:
Temperature is a measure of the average (kinetic) energy of the particles which make up some material
Power is measure of energy transferred per second (J/s)
The temperature of the filament in a ...
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2
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445
views
Does current density from a wire same in smaller cross section?
To be more simple, If current $i$ is flowing through a long cylindrical wire does the current density of region $A$ and $B$ same?
user305073
1
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2
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766
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What force moves electrons through a conductor that is rotating in a magnetic field [closed]
Is it the magnetic force ( F= qv +B ) or the electromagnetic force (F= q(E+vxB) that acts on the electrons of a conductor that is moving in a magnetic field?
Thanks.
user232620
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393
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Potential difference across two points in a current-carrying wire [duplicate]
I have had this doubt for quite a while and I have tried reading answers to similar questions but I'm still not sure.
If I connect a voltmeter at A and B, what would be the reading? Is it going to be ...
user287374
2
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2
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3k
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Why is high voltage more deadly than low voltage?
Why is higher voltage said to be more dangerous? Doesn't higher voltage decrease current as P = IV where P is constant, thus making it less deadly?
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