All Questions
173 questions
0
votes
1
answer
85
views
What is resistance precisely?
Is there a mathematical definition for resistance because I cannot find any. On the internet I find definitions such as:
The electrical resistance of an object is a measure of its opposition to the ...
- 213k
1
vote
2
answers
293
views
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 ...
CommunityBot
- 1
-1
votes
0
answers
16
views
Speed of current at higher and lower potential [closed]
It is said that, charge has more potential energy at higher potential as compared to lower potential in an electric circuit. So, is the speed of current faster at higher potential and slower at lower ...
1
vote
1
answer
307
views
Is there a potential difference across the bulb after current passed through a diode?
I understand that voltage can exist without current so what I want to ask is will there be a potential difference across the bulb(situated after the diode) when a batteries supplied energy through a ...
CommunityBot
- 1
13
votes
5
answers
4k
views
Watts vs. volts amperes
What I understand:
In simple DC circuits, this is a product of the current and voltage, such that 1 watt = 1 ampere x 1 volt
I understand that a watt is a unit of power (change in energy per unit ...
11
votes
3
answers
5k
views
Why high voltage transmission lines?
This is a question which I seem to have tackled multiple times, solved each time after reading a dodgy internet explanation, then partially forgotten about and retackled half a year later. It is time ...
- 6,269
5
votes
2
answers
140
views
What is the "closed circuit" of a bug swatter racket?
There are bug swatter racket that can kill fruit flies, mosquitos, or flies, if the insect touches the metal mesh.
However, when I look at the construction of the device, the metal mesh is all one ...
- 213k
5
votes
4
answers
38k
views
Among current and voltage which is responsible for brightness of a bulb?
In a circuit that is fitted with a bulb, which is the factor that affects brightness of that bulb: current in the circuit or the voltage offered by the battery in that circuit?
- 462
0
votes
1
answer
38
views
Ideal Superconductor connected to Zero Voltage
If an ideal superconductor was just left alone, with no potential difference, what would be the current flowing in it?
According to Ohm's Law, $V = IR$
Hence, if a superconductor of $0\Omega$ ...
- 109k
0
votes
2
answers
61
views
Piece of iron instead of a proper fuse
In a video game Dying Light 2, there are those electrical boxes that you open and then "fix" by putting a piece of iron (I suppose). Assuming voltage $U$ is being produced and is supplied ...
- 6,980
0
votes
2
answers
226
views
Explanation of Potential Difference
My question is to verify if my thought process below is correct.
So in a circuit the charge will flow (the current). When the charge flows there is resistance which is the collisions of the charge ...
- 719
21
votes
8
answers
14k
views
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 $...
- 2,085
0
votes
3
answers
121
views
Why won't the bulb light? [closed]
Here's what the marking scheme says: "Capacitor gets charged first and acts as an insulator/blocks current".
However, electrons flow from negative to positive, so shouldn't the electrons ...
- 16.2k
0
votes
3
answers
126
views
Potential drop against internal resistance of cells in combination
Suppose two cells of emf and internal resistance e1, r1 and e2, r2 respectively are connected in series. The negative electrode of 1st cell is connected to negative electrode of the second cell. Why ...
- 99.9k
1
vote
4
answers
1k
views
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 ...
0
votes
1
answer
654
views
Understanding the physical meaning and effect of voltage and current being out of sync
In alternating current, we may have inductors and capacitors which make voltage and current become out of sync.
At the beginning, I was stuck because how can it be that there is first voltage and ...
- 213k
0
votes
1
answer
460
views
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 ...
- 33
1
vote
3
answers
1k
views
Does current make the full return trip?
In an AC system, the neutral wire is said to provide a return path for the current back to it's source. Given that the current is said to be alternating back and forth, how does this work, does the ...
- 494
0
votes
1
answer
39
views
When using a screwdriver tester i am completing the circuit with 110v?
if i use a screwdriver tester, i am part of the circuit with 110v passing my body? isn't this dangerous?
- 213k
0
votes
1
answer
80
views
"Why do power lines use high voltage?" Loss in power equal to Current*Voltage? [duplicate]
I define P is the average power. So $P=IV$ and $I=\frac{P}{V}$.
$P_{loss}$ I define to be the power loss, which is equal to $I^2R$.
Substituting for $I$, $P_{loss} = \frac {P^2R}{V^2}$
So I get that ...
- 56.5k
9
votes
5
answers
4k
views
Why is it easier to raise AC current to high voltage than DC?
In my country (and maybe all around the world I don't know) once electricity has been generated, it is then raised to 200k Volts for transportation.
I know this is to reduce the loss. Given $P=U.I$ ...
- 1
1
vote
1
answer
56
views
Potential divider problem [closed]
What does the curved arrow represent? The answer states that L1 will be dimmer than L2.
From my current knowledge, moving the contact K closer to X will somehow increase the voltage of L2 meaning it ...
0
votes
2
answers
357
views
Voltmeter connected to parallel circuit
This is my current understanding. Voltage is defined to be the potential difference between 2 points, hence it only makes sense for a voltmeter to be connected in parallel. But why must this voltmeter ...
- 77.9k
1
vote
1
answer
124
views
Transformers in Power transmission [duplicate]
Recently I learnt that transformers are used in the national grid to increase the voltage, so we get less current. But my understanding V=IR and by increasing the voltage we get more current, so what ...
- 36.6k
0
votes
3
answers
1k
views
How does current actually flow in a wire?
When I was in my school I was taught that the electric field due to the battery is along the wire (from $A \rightarrow B \rightarrow C \rightarrow D $) and these are responsible for electrons at each ...
- 195
12
votes
2
answers
2k
views
Which electrons kill you during electrocution?
I understand that there are three velocities in play in a circuit (I haven't studied Physics past high school so give me some rope)
v1: the velocity by which the electrical field propagates through ...
- 213k
1
vote
1
answer
229
views
High voltage in transmission line [closed]
I'm trying to understand why high voltage is used in transmission but I seem really confused by the explanations I read.
Here's what I could make out:
$$P_\text{loss} = \dfrac{ΔV^2}{R_t} = \dfrac{(...
- 349
0
votes
1
answer
97
views
Does an open circuit have electrons accumulate in it?
This is what I have imagined electricity to be like, where the blue balls represent the free valence electrons in a conductor atom, and the electrons flow towards the positive electrode as the ...
- 99.9k
1
vote
3
answers
125
views
$I$ proportional to $V$ or vice versa?
I am confused whether Voltage depends on current or the vice versa. I always thought that the vice versa was correct. I tried to find the answers of some of my other conceptual doubts on the web but I ...
- 425
9
votes
5
answers
4k
views
How does the electrical ground rod work?
I was reading this article about shock current path, but it seems to be contradicting answers that I have seen on this site regarding electric shock. I can't find the original question but it was ...
- 16.2k
1
vote
1
answer
2k
views
Why increasing the resistance in a series circuit decreases the current in the circuit?
Concise Physics mentions that:
On connecting one more appliance in the same circuit , the resistance
of the circuit will increase . Hence , it will reduce the current in
the circuit , so each ...
- 6,641
-1
votes
2
answers
223
views
How does the high potential difference between the two points ionizes the air?
As we can see that for some instance air can tolerate the potential difference between two points without any high leakage current and when this potential difference between the two points becomes too ...
- 30.2k
7
votes
5
answers
3k
views
How does a resistor "know" to increase the potential difference across its ends?
My book says that current has to be constant throughout a simple series electrical circuit consisting of wires, a cell and few resistors, and hence resistors have higher potential difference across ...
- 15.5k
0
votes
1
answer
47
views
Confusion regarding drift velocity and potential
From this post I understood that the drift velocity of electrons decreases further into the circuit. But my book says that electrons move with constant velocity throughout the circuit, and both of ...
- 36.6k
0
votes
1
answer
200
views
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 ...
- 36.6k
-1
votes
1
answer
411
views
Not enough current to supply load
Are there cases where a power supply can offer xV, which is required by a device, but be unable to supply enough current?
For example, a voltage divider not only lowers voltage, but limits the ...
CommunityBot
- 1
0
votes
2
answers
700
views
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 ...
- 6,797
20
votes
4
answers
5k
views
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) ...
2
votes
2
answers
671
views
Ohm's law and Joules heating
Ohm's law state that the ratio of V and I gives us a constant value of R provided that the temperature is kept constant throughout. However, in accordance with the joule's heating it would get heated ...
- 58.6k
0
votes
1
answer
273
views
Power and power loss during transmission of power
So let's say power to be delivered to homes is 80 kW($P_3$ = 80 kW) and the houses have to receive it at 220 V ($V_3$ = 220 V). The substation is a 4000 V to 220 V step-down transformer and $R_2=15\ \...
- 213k
2
votes
1
answer
606
views
Power loss in power cable contradiction
To minimize the power loss in long-distance power cables it is best to minimize the current and maximize the voltage. This is because the power loss in the cable is calculated by $P=VI$, which we can ...
- 213k
11
votes
1
answer
2k
views
High voltage power lines - clarification of energy loss
I've been having a bit of trouble understanding the high-voltage power lines. If I was sending power from $A \rightarrow B$, we have:
Ohm's law $V = IR$
Power lost in the form of heat $P = I^2 R$
...
- 2,350
1
vote
2
answers
40
views
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 ...
- 4,936
2
votes
2
answers
3k
views
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?
- 5,197
1
vote
2
answers
154
views
On a nanoscopic level, what really happens to the electrons in the secondary coil of a step-up transformer?
I know that when AC is passed through the primary coil of a step-up transformer a higher emf is induced in the secondary coil (with more turns) of the transformer. Since energy is conserved, and P = ...
- 10.8k
2
votes
2
answers
184
views
Confusion over Van de Graaff vs. Electric Fence
It is said "It is not the volts that kill you, but rather the current".
However, volts is directly related to current as V= IR (current x resistance).
Since the resistance of one particular ...
- 7,876
9
votes
3
answers
8k
views
When the voltage is increased does the speed of electrons increase or does the electron density increase?
I am just a high school student trying to self study, please excuse me if this question sounds silly to you.
I know that current is a product of the speed of electrons and the electron density.When ...
8
votes
5
answers
73k
views
What is the voltage of an average carpet static shock? Can you make it lethal?
I think I heard somewhere that it was in the thousands of volts, but it had extremely, extremely low amps. Could you somehow transform the current to make it larger or something? Or does the equation ...
- 1,652
0
votes
0
answers
53
views
Does a bulb offer still offer resistance even after it gets fused? [duplicate]
Sorry, for my naivety this is my first time posting here.
But, my question is that will the bulb offer any resistance after it's fused?
I know that no current can flow though the fused bulb i.e. $I=0$....
- 2,349
14
votes
8
answers
110k
views
What causes an electric shock - Current or Voltage?
Though voltage and current are two interdependent physical quantity, I would like to know what gives more "shock" to a person - Voltage or Current? In simple words, will it cause more "electric - ...
- 338