Questions tagged [electrical-resistance]
The tag applies to electrical resistance and resistors. DO NOT USE THIS TAG for non-electrical resistance.
2,277
questions
-1
votes
3answers
92 views
How does current get reduced in resistor?
How does the resistor reduce the current? I know that when there is no resistor in the circuit the current is higher than the current when there is a resistor.
But, my question is:
How the resistor ...
1
vote
1answer
47 views
How long does a headphone last on a given battery? [closed]
Sennheiser HD 598 has 50Ω impedance. It has a 3.6mm cable, but I am planning to do a simple DIY project to replace the cable with a bluetooth receiver, a 3.7V 1000mAh battery (and a charging board).
...
-2
votes
0answers
28 views
Current in an resistor [duplicate]
Suppose I have a electric circuit as shown in image
Let a resistor is connected to a battery. The current starts flowing through the resistor.
Why is the current entering the resistor the same as the ...
0
votes
1answer
42 views
High voltage in electric power transmission systems - why Ohm law is used regardless of "assuming the power is completely converted into heat"?
Similar questions feature found about 10 QA's here on the subject with all about 1-5 cumulative upvotes. For example Why do power lines use high voltage? have 6 upvotes for accepted answer:
The line ...
-2
votes
0answers
22 views
What will be the currents through $R$, $L$ and $C$ at $t=0$ + (The complete question's provided in the image attached below)? [closed]
Choose the suitable alternative(s)
Elements R, L, C are connected in parallel and excited by a DC source of l Amp. If
IR. iL and ic are the currents through R, L, and C respectively. then at t=O+
i) ...
-1
votes
1answer
39 views
How can current be constant and still result in resistors having a voltage drop?
My issue arises when thinking about the situation like this. Current is the amount of charge flowing through an area, and resistance is basically they difficulty in doing so. My issue results when ...
1
vote
2answers
51 views
Can I apply Kirchhoff's current law to two separate nodes which are connected only by an ideal wire? [closed]
Suppose there are 2 nodes A and B in the above circuit. If A has 2 incoming currents $I_1$, $I_2$, and B has 1 incoming currents $I_3$, $I_4$, is it correct to write the equation of whole nodes and ...
0
votes
2answers
35 views
Maxwell’s first equation in conductor we take E=0. And I have read that’s true for practical time scales. But in 4th equation we use non zero E, why?
\begin{align}
\nabla\cdot E&=0\\
\nabla\cdot B&=0\\
\nabla\times E&=-\frac{\partial B}{\partial t}\\
\nabla \times B&=\mu J+\varepsilon\mu\frac{\partial E}{\partial t}=\mu\sigma E+\mu\...
-2
votes
0answers
29 views
Resistance of a wire doesn't depend on which of the following? [closed]
I don't know the answer of this question everything answer look same so please answer this
3
votes
2answers
818 views
What potential difference or current would kill a person?
I was watching this YouTube lecture, and earlier in the vid he mentions 120 volts from a power outlet would kill you. So if human resistance is $300\ \Omega$, $0.4 \rm A$ should be enough to do the ...
0
votes
1answer
37 views
Is electrical resistance analogous to friction?
In a circuit, an electric field is produced from a circuit element providing a voltage source. Electrons flow through the circuit undergoing collisions which provide a resistive force to the electrons ...
1
vote
1answer
53 views
Circuit problem [closed]
Hello, can someone please help me on this problem?
Question: calculate the potentials at A and B.
The solution says that they are both 12V "due to symmetry" but I have no idea what is the ...
2
votes
4answers
358 views
What good reason to hang long cable carrying electric current high above the ground? [closed]
Assume no flooding or other natural disasters to damage the cable if it is laid beneath the ground, then what good reason for them to be suspended high above the ground? The cables are insulated and ...
0
votes
1answer
21 views
Temperature coefficient
If we raise the temperature of any conductor the atom, free electrons starts vibrating
There kinetic energy increases
If kinetic energy increase then , Current must be increase
As current increase ...
1
vote
1answer
43 views
Does the resistance of a filament lamp change?
Recently in a work book there has been a question to explain with the aid of a circuit diagram the method a student could use to investigate how the resistance of a single lamp changes with potential ...
0
votes
2answers
29 views
I don't understand why for resistors in AC circuits the phase angle between voltage and current is zero
From the following graph I understand it is because they reach the voltage and the current reach their maximum values at the same time on the resistor, but I don't understand why this should be that ...
0
votes
1answer
40 views
Huge current flows when there is no resistance, consequently, the potential difference is 0 but no current flows if no cell is added to the circuit
If $R= 0$ , $V= 0$ and $I=$ $max$ (i.e. charges are flowing at a huge rate), but when there is no potential difference applied to a circuit, charges don't flow. That means huge current flows when ...
20
votes
4answers
4k 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) ...
1
vote
1answer
39 views
What would happen if we were to put a resistor at a junction?
I am currently studying electrical circuits in high school, and at some point I wondered what would happen if we were to create three (or more) connections on a component and put it at a junction. For ...
0
votes
2answers
30 views
Voltmeters / direct measurement of voltage in a circuit
I was wondering that many instruments that measure the ddp in a circuit works measuring instead current and then applying Ohm's law.
When I looked for how Ohm made his initial measurements for voltage,...
0
votes
0answers
32 views
Is effective EMF always greater or less than individual EMFs?
When we connect many Resistors with Resistance = $R_{i}$ in series, we get an equivalent resistor with resistance equal to $R_{eq}=R_{1}+R_{2}+R_{3}...$
This logically implies that the equivalent ...
-1
votes
1answer
23 views
What are the steps that give rise to this following resistance equation for a diffusive transport of electrons?
$ R = R_b (1 + \frac{\lambda}{L})$
Source - page 6 of this book: https://nanohub.org/courses/FON1/01a/asset/15698
0
votes
1answer
46 views
Why my electromagnetic coil generates a weak field and increase its resistance when I use higher voltages? [closed]
I've been trying to build a coilgun, so I winded a cable around a 7cm long pvc tube (the diameter is 2 cm). The cable is composed of about 30-35 parallel wires so I calculated the general resistance ...
-1
votes
0answers
22 views
Is the terminal voltage twice the EMF when the battery is being charged and short circuited?
So, I know V terminal= E- Ir during discharging of a battery. 'E' is the EMF, 'r' is internal resistance of the battery and 'I' is current.
If the battery is short circuited, 'I' becomes = E/r because ...
0
votes
1answer
45 views
Why can't both the formulas $I^2R$ and $V^2/R$ be used to find energy lost in a supply cable?
-1
votes
2answers
60 views
Is there anything other than Resistance, Capacitance, Inductance in a circuit? [closed]
Resistance, Capacitance and Inductance measure certain electrical property of some matter. These term have even given rise to objects like resistors, capacitors and inductors respectively.
Few ...
0
votes
1answer
21 views
How does the conductivities of metals and semiconductors vary when placed in the presence of magnetic field?
Suppose you have two materials one is a metal and other is a heavily doped semiconductor and they are placed in a magnetic field. What experiment will you do to distinguish between them? Does the ...
1
vote
3answers
43 views
What is the significance of Power factor?
I was studying the power in Alternating current. The formula to calculate the power in alternating circuit is
$$P = VI \cos{\Phi} $$
where, $V$ and $I$ are RMS values of voltage and current and $\Phi$ ...
0
votes
0answers
25 views
Modelling electrical conductivity in low-dimensional nanostructures
I know that the Boltzmann transport equation can be solved under the Relaxation Time Approximation (RTA) to obtain the electrical properties of materials. However, the parameter that I am interested ...
0
votes
0answers
35 views
EM waves with complex conductivity
In the solution of Maxwell equations inside conductors,
$J=\sigma E$ is used.
In the derivation of e.g phase difference, and skin depth, $ \sigma$ is assumed to be real, e.g
$e^{-b\cdot r}$ is the ...
2
votes
2answers
230 views
Ohm’s law holding true on temperature-dependent resistances
As far as I know, Ohm's law (in macroscopic form) states that the in some devices/conductors/materials, the (instantaneous) current through the device is directly proportional to the (instantaneous) ...
0
votes
1answer
77 views
Why does the potential of both power supplies drop when only one is needed to maintain the current?
In the circuit shown above, the current through the ammeter is the sum of the currents through each power supply. By Kirchoff‘s Voltage Law however, we can treat each power supply to be in an ...
8
votes
5answers
2k views
Why does a drop in resistance lead to a drop in voltage?
I was working on this question which I know the answer to but I am still confused. I get that resistance is due to collisions on the atomic scale where the electrons' kinetic energy is transferred to ...
0
votes
4answers
47 views
The relationship between impedance, resistance and resistivity and which are purely material properties
The resistivity of a wire, $\rho$, is purely a material property. For a wire of length, $l$, and cross-sectional area, $A$, the resistance, $R$, is given by
$$
R=\frac{\rho l}{A}
$$
which depends on ...
0
votes
2answers
85 views
British Physics Olympiad Round 1 2010 Q2a - Find potential difference between A and B [closed]
I've been trying some British Physics Olympiad past papers. In the 2010 Section 2 paper, the first question is the following:
I've never seen a circuit like this, and I'm unsure what the correct ...
0
votes
2answers
87 views
A circuit with 2 resistors in series - current in between them
Let us have this circuit:
We know from Kirchhoff's laws that the current I1 entering R1 and current I3 exiting R3 are the same, I1=I3.
But the point that bothers me is that: we know according to Ohm'...
1
vote
1answer
101 views
Resistor Cube Problem Intuition
In the well-known resistor cube problem using a resistor cube with equivalent resistors on all the edges, the prescribed approach to solving it involves merging points of equivalent potential as shown ...
0
votes
1answer
34 views
Resistance of a resistor - dividing infinitisimals [closed]
Given a resistor with the shape of half a sphere with inner radius of $R$ and outer radius of $3R$.
The sphere has a conductivity of $\sigma(r)=\frac{\sigma_0 R}{r} $.
A current is inserted in the ...
11
votes
3answers
1k views
Why are potential drops concentrated at resistive elements?
I do not understand why potential differences in the electric field in a circuit are concentrated at resistors when the potential, to my knowledge, is purely dependent upon location in the field and ...
0
votes
2answers
61 views
At absolute zero temperature, we see that the electrical resistivity of a metal is not zero - Why? [closed]
I do know that for a perfect conductor, the electrical resistivity is zero at absolute zero temperature. But for an imperfect conductor (e.g. that we use in daily life) it is not zero even at $T=0^{\...
0
votes
4answers
66 views
Finding Voltage of a Circuit [closed]
I am self studying circuit analysis, and got the following question wrong:
Since the 12 Volt battery's negative terminal connects to ground, V1 must equal 12.
The current i should equal the voltage ...
0
votes
0answers
39 views
Errors in Drude model for thermal conductivity in metals
According to the Drude model the thermal conductivity comes out to be
$\kappa = \frac{1}{3}v^2\tau c_v$ the derivation of this is given in wikipedia also there it is mentioned about the errors made in ...
9
votes
3answers
3k views
I Do Not Understand a Textbook Example: Calculating Voltage Across a Resistor
I am reading Agarwal and Lang's Foundations of Analog and Digital Circuits for self study, and I do not understand one of their illustrated examples (specifically, example 2.14).
They present this ...
0
votes
1answer
29 views
Intuition behind phase difference in AC circuits
So I've been studying AC Circuits lately and I've come across a few things that I'm not able to digest. Let's take a pure inductive circuit for example.
This is the first time I'm experiencing current ...
0
votes
2answers
73 views
Electron flow across a wire depending on the Resistance across it [duplicate]
In my grade 10 Physics book, its written that the electrons collide with the positively charged particles in the resistor and-
These collisions tend to slow down the speed of electrons and hence ...
0
votes
1answer
32 views
A problem on Alternating Current Related with Bulb's Brightness
I was going through some problems of Alternating Current [High School Level] and one of the questions asked
'A coil of self Inductance $L$ is connected in series with a bulb and An AC source. ...
-2
votes
1answer
32 views
Calculating voltage given other voltages in a circuit [closed]
I am self studying circuit-analysis, and got the following question wrong.
I thought the answer was c, but it is actually d. Could anyone explain why?
1
vote
2answers
118 views
Finding current in a circuit of a transformer
I was taught transformer yesterday and my teacher had given me a question of a step down transformer. The question states that
The Power input into the transformer is $10kW$ and the voltage of the ...
0
votes
2answers
30 views
Does a resistor make also a higher physical resistence to el. current along with more chemical resistence than does a conductor? [closed]
Does a resistor make also a higher physical resistence to electric current along with more chemical resistence than does a conductor? Asking so because of the fact that a resistor is always the ...
0
votes
1answer
49 views
How does a resitance affect electric current in a circuit...??(series)
Consider the following circuit:
Let the resistance of the lamp be $R_1$, and the potential difference across it be $V$. Let the current that flows through the circuit be $I$ in this situation. Say you ...
