Tagged Questions
-1
votes
0answers
24 views
Increasing Amps [closed]
I am not sure if this is the place to post this, but both physists and electricians should be able to help here, so I am going to cross post with DIY (sorry if this really annoys people - I know it ...
1
vote
1answer
26 views
Why should a battery not give current in order to measure EMF?
Emf is the "potential difference (PD) across the terminals of a battery when it is giving no current to the circuit."
What does "when it is giving no current mean"? Will the PD across the terminals ...
0
votes
1answer
46 views
Volts, Amps, and Practical Electrical Knowledge
I've heard people say that high amperage or high voltage is dangerous to humans-aren't they both? And what are the advantages to high amperage versus high voltage? And how do you generate one or the ...
1
vote
1answer
21 views
Speakers and Static from Hands
Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?
1
vote
2answers
90 views
Simple ohms law on a battery ? Paradox or conceptual error?
Suppose we have a regular pencil battery which supplies DC voltage $V$. Say we take copper wire and connect the ends of the battery to an $R$ ohms resistance.
Then Ohm's law tells use the current in ...
2
votes
1answer
113 views
Is it possible create current by spinning a charged sphere?
If we have a sphere which has $σ$ surface charge density and rotate it in axis z will this create current ? Is it possible without any potential difference ?
1
vote
2answers
46 views
Light bulbs, Wattage meaning? [closed]
Light bulbs, Wattage meaning?
Two incandescent bulbs (120 V, 25 Watt) and (120 V, 500 Watt) connected to the same batteries.
Which one shines brighter? And why?
2
votes
0answers
57 views
Current between supeconducting rings
How to calculate the current between two superconducting rings with radius r separated by a distance d?
Please note that being unfamiliar to the concept of superconducting rings, I can't approach ...
0
votes
1answer
71 views
AC passed to a DC motor
What would happen when an alternating current (AC) is passed to a DC motor? And a direct current (DC) passed to an AC motor?
Will it work or not?
What will happen to it?
4
votes
3answers
575 views
Why is AC more “dangerous” than DC?
After going through several forums, I became more confused whether it is DC or AC that is more dangerous. In my text book, it is written that the peak value of AC is greater than that of DC, which is ...
1
vote
3answers
150 views
How exactly does a resistance reduce current?
I've heard that resistors are used to decrease current to a particular appliance, such as in the regulator of a fan. However, I've also heard that the total current in a circuit is always the same- in ...
0
votes
0answers
43 views
Object accelerated by electromagnet
If I have an electromagnet (powered by a battery) and a metallic object, the
power generated will depend on the voltage of the battery and the resistance of the coil.
If I accelerate the object, will ...
2
votes
2answers
304 views
Round bulb and Long bulb in Series Circuit
If you have a series circuit with a battery, one round bulb (with thicker filament), and one long bulb (with thinner filament), the round bulb does not light up and only the long bulb lights up.
...
3
votes
2answers
416 views
Capacitor circuits with light bulb
Let's say we have a normal circuit with a light bulb, with wires and a battery.
When one places a capacitor in this circuit, how is the light bulb able to light up, even when the capacitor prevents ...
2
votes
1answer
88 views
Which of these two methods is correct for calculating current?
I recently came across a question, for which I saw two possible methods of finding the solution. I was required to calculate the "current flowing" $I$ when given the voltage $V$, frequency $f$, total ...
2
votes
2answers
578 views
Ohmic and Non-Ohmic devices
Why do some conductors follow Ohm's law and some do not? Isn't there any universal law that can explain the flow of current?
2
votes
2answers
207 views
Why does the current stay the same in a circuit?
I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
1
vote
2answers
103 views
Under what condition charges do not flow in closed circuit?
I wanted to ask under what conditions will charges not flow in a closed circuit. Or when is current through the circuit zero even when an EMF is applied?
Like in the case of potentiometer, we say that ...
1
vote
1answer
197 views
What kills you: Voltage or Electric current? [duplicate]
Possible Duplicate:
What causes an electric shock - Current or Voltage?
When someone gets electrocuted, what kills them; a high Voltage or a high Electric current, and why?
1
vote
1answer
147 views
What does the current vs voltage graph of a halogen look like?
I have a halogen light with a tungsten filament. It is rated 500w at 130v but I am running it from an inverter in my car that is putting out 110v. I would like to know what the actual power usage of ...
3
votes
3answers
407 views
Where do electrons in electricity come from?
Where do the electrons come from when an electric generator is making electricity? Is from the air? Would a generator work in a vacuum? Electrons have mass so where would they be pulled from if ...
2
votes
3answers
662 views
is it possible to flow current in open circuit?
First , i don't know much about chemistry and physics. I'm just a graphic designer but i have this question in my mind. I'm sorry if this question is too basic and use 'generic' language.
As i know ...
4
votes
2answers
322 views
How to calculate required current and specifications for a “wet coil” to generate x Tesla of magnetic field?
A water management project requires a "wet coil" (coil will be submerged in aqueous media) designed to generate a steady-state electromagnetic field of adjustable magnetic magnetic flux density at the ...
0
votes
2answers
548 views
Confusion about P=VI and V=IR
If we look at $P=VI$, we see that if the current doubles then the potential difference is halved
but this doesn't seem to make sense according to $V=IR$. If we look at that equation, since the ...
1
vote
1answer
115 views
Electromotive force
EMF is defined as:
"The potential difference across the terminals of a battery or dry cell when it is giving no current to the circuit."
So, if current starts to flow from the ...
4
votes
4answers
371 views
Are square wave really square or are they always relative approximations using harmonics
I'm studying the properties of waves through different mediums, and got hung up on this.
Is a square wave always a sum of harmonics or can we produce a square wave by quickly changing voltage? Is ...
1
vote
2answers
715 views
Basic questions about voltage drop in DC circuit
I understand all the concepts of what voltage is using all the analogies but some things related to the drop of voltage across a circuit confuses me.
If I had a short circuit and attached a ...
1
vote
2answers
2k 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 ...
0
votes
1answer
177 views
What does a positive gradient on a graph of V plotted against I mean in terms of EMF and internal resistance?
According to the equation $V = E-Ir$, the gradient of a graph of $V$ against $I$ should be $-r$ (internal resistance) and the Y intercept should be the EMF. Am I right?
In an experiment I used a ...
3
votes
3answers
4k views
Why do birds, sitting on electric wires, not get shocked?
If we would touch electric wires, we would get a shock, even if we are not touching ground (so that no connection is complete form wire to ground through us). I always see that birds sit on electric ...
0
votes
1answer
175 views
Capacitance and Light Bulb And Dielectric Slab [closed]
An electric lamp having coil of negligible inductance connected in series with a
capacitor and an AC source is glowing with certain brightness. How does the
brightness of the lamp change on reducing ...
3
votes
6answers
3k 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 - ...
0
votes
1answer
85 views
Why is the anode (+) in a device that consumes power & (-) in one that provides power?
I was trying to figure out the flow of electrons in a battery connected to a circuit. Conventionally, current is from the (+) terminal to the (-) terminal of the battery. Realistically it flows the ...
0
votes
1answer
100 views
How to measure electrical resistance?
Is it possible to theoretically measure the resistance of passing of electrical current through liquid electrolyte (distilled water + NaOH) ?
1
vote
2answers
296 views
Calculate power $P=V \times I$
I have an adapter which mentions like this...
Input: 100-240V~1.8A
50-60hZ
So how much power does it really consume?
I just knew ...
1
vote
1answer
143 views
Residual Resistivity in alloys and metals
Residual Resistivity
I saw that the graph of resistivity to temperature of alloys like nichrome is like so
Meaning that even at 0 K it has some resistivity just like copper :
I read some where ...
1
vote
2answers
171 views
Fundamentality of voltage to current
From Ohm's Law :
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.
I would like to know if ...
4
votes
6answers
5k views
In an alternating current, do electrons flow from the source to the device?
If electrons in an alternating current periodically reverse their direction, do they really flow? Won't they always come back to the same position?
2
votes
1answer
527 views
How does a voltage independent current source work?
So I'm having some trouble understanding what a voltage independent current source is. How can you have a current without a voltage. as I understand it voltage or EMF is the force that drives the ...
1
vote
1answer
2k views
Current against the inverse of resistance graph, $I = V/R +c$
If I have a plot of current ($y$ axis) against 1/Resistance ($x$ axis).
The circuit it is measured from is a simply 2 resistors connected in parallel to battery, where the potential across the ...
11
votes
4answers
2k views
Why is the charge naming convention wrong?
I recently came to know about the Conventional Current vs. Electron Flow issue.
Doing some search I found that the reason for this is that Benjamin Franklin made a mistake when naming positive and ...
4
votes
6answers
6k views
Difference between current and voltage sources
I am confused about the current and voltage. My intuitive example would be that of a pipe of say water. The diameter of the pipe determines the amount of water flowing per second but the pressure is ...
