0
votes
1answer
15 views

Can a current source provide Voltage to a resistor?

We know that the tension between a perfect current source is 0 We have Va-Vb= 0 but we also have by ohm's law Va-Vb=RI=5V so 5 = 0?
7
votes
3answers
816 views

Which dissipates more power, a small or big resistor?

I was talking to someone about trying to dissipate the most heat from a metal crucible (essentially just a resistor $R$). He argued that you wanted the resistor to have a high resistance because ...
3
votes
2answers
58 views

What exactly is resistance and Ohm?

Ohm is defined as "a resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere, the ...
1
vote
2answers
78 views

Voltage and resistors

I've read in many books and through many answers on this and other sites about this concept. Now I'm not sure what to "believe". In the subject at my university, we are taught that conducting wires ...
1
vote
1answer
44 views

Calculate the equivalent resistance between A and B [closed]

Find the equivalent resistance between A and B. I tried using nodal but there were too many unknown variables. Please help. Thank you!
4
votes
2answers
172 views

Voltage drop due to a resistor

I'm afraid this question is going to sound rather dumb but here it is: Suppose I have a very simple circuit: one battery and one resistor. The sum of the voltages in this circuit has to equal zero. ...
1
vote
3answers
94 views

Why is equivalent resistance in parallel circuit always less than each individual resistor?

There are $n$ resistors connected in a parallel combination given below. $$\frac{1}{R_{ev}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+\frac{1}{R_{4}}+\frac{1}{R_{5}}.......\frac{1}{R_{n}}$$ ...
1
vote
2answers
50 views

What is the difference between a circuit with a resistor and one without it in energy terms?

In Fundamentals of Physics (HRW), an equation is derived for the current in a circuit in terms of its emf and resistance by the 'Energy method'; that is, deriving emf=i.r and saying that the work done ...
7
votes
2answers
437 views

Can resistance be directional?

When we think of resistance, we always think of a scalar value associated with a piece of a material. After all, resistance is but resistivity times surface geometry. But can resistance be ...
1
vote
2answers
51 views

Finding the current in a parallel circuit [closed]

Two resistors are joined as shown. The top resistor receives a current of 3 A. What is the current in the other resistor? What is the current that enters at junction A? I'm confused on how the two ...
0
votes
2answers
24 views

Direction of current in concentric cylinders

Example 7.2 in David Griffiths E & M book (3rd edition) has a side view of 2 concentric cylinders, with smaller radius $a$ and larger radius $b$. The region in between $a$ and $b$ has ...
2
votes
4answers
85 views

Why does a Resistor cause a potential drop?

I need to know the underlying physics of what exactly happens different with the electric field in the resistor than in superconducting wires. Why is it that when I connect a resistor, potential ...
1
vote
0answers
13 views

Why is low resistance beneficial to ion exchange membranes?

http://scitation.aip.org/content/aip/journal/jcp/139/11/10.1063/1.4821161 The article states that the graphene filter has a much lower electrical resistance than existing ion exchange membranes, ...
0
votes
3answers
168 views

Why does resistance increase with length?

This is for the case of wires only (pipes are easy). I see that if I place a 9-Volt (constant) battery across any wire, the current is proportional to resistance. I don't understand why, for a ...
1
vote
2answers
117 views

Why isn't resistance proportional to distance squared

Here we have a wire. At both ends there is an equal and opposite field caused by a chemical reaction. So, if we decrease or increase the distance between the two points, the strength of the field ...
1
vote
3answers
71 views

What really is resistance? How does it generate heat?

OK I know that R= V/I. I also know that R = ρl / A But what I want to know is that what really causes resistance? Is resistance equivalent to force? or is it just a constant? Also, what causes ...
0
votes
1answer
59 views

Simple Parallel Electric Circuit [closed]

Ammeter (A1) and voltmeter (V) in series have parallel connection to another ammeter (A2). Currents in A1 and A2 are respectively 0.2 and 1.7 amp. Voltmeter's voltage is 6 volts. How should I find ...
0
votes
3answers
81 views

Could this open electric circuit work?

Two batteries are interfaced by a resistor. Parameters such as resistance can be set arbitrarily. Does it work?
3
votes
2answers
228 views

How is the current same on both the sides of a resistor?

I am wondering that how can current be equal on either side of a resistor as the work of a resistor is to resist the flow of electrons i.e. decrease the current. How is this possible?
-3
votes
2answers
59 views

Other units of resistance [closed]

Resistance is $\frac{V}{I}$, and we get the unit $\Omega$. Another unit is $\frac{W}{A^2}$. How do you derive that unit?
1
vote
1answer
56 views

Circuits and Power

"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest? a) V only b) V and W ...
3
votes
3answers
198 views

If the current is increased, is there more charge flowing or is it moving quicker?

Problem Current is the amount of charge that is flowing through a component per unit of time. For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must ...
1
vote
1answer
335 views

The shape of the graph of the equation: $V= -r I + E$

I have recently collected data (for a school experiment) in order to measure the EMF and the internal resistance of a solar cell. The data complied with the equation: $V = -rI + E$, i.e. the voltage ...
0
votes
0answers
235 views

What would the graph between P (power) and i (current) look like if the graph between V (potential difference) and i is parabolic?

The answer is same... That us the graph between P and I will also be a parabola.... Similar to the graph between V and I. But how? Can anyone explain through mathematical approach ? I used ...
0
votes
1answer
306 views

Why does material resistance increase with temperature but electrolyte internal resistance decrease with increase in temperature?

The question is pretty much in the title itself, why does the internal resistance decrease with the increase in the temperature of electrolyte? Is it related to the electrolyte bring a fluid or ...
0
votes
1answer
380 views

Does a resistor absorb and dissipate energy or just regulate the charge flow?

I've this doubt regarding resistor: suppose I make a simple circuit with a power generator of 3 Volts and 1 Ampere and a resistor of $10 k\Omega$ I know from Ohm law that the current flow $i$ is: ...
2
votes
1answer
95 views

Do batteries lose charge?

Say I have a charge of +q and -q on the positive and negative terminals of a battery. If I connect wires to each terminal, but don't connect the wires (essentially creating an open circuit), the ...
0
votes
0answers
71 views

Resistance of a cylinder contacted by two smaller circular faces

Suppose we have a solid homogeneous cylinder with radius $a$, heigth $h$ and conductivity $\sigma$. The top and the bottom face is contacted with a smaller circular face with radius $b$. How can I ...
2
votes
1answer
344 views

How do capacitors work?

Say you have a battery, with a wire connecting the negative and positive terminal. Initially, (the transient state) the electric field is not uniform and is perpendicular to the surface of the cross ...
8
votes
4answers
197 views

Temperature and resistance?

Why does resistivity increase with temperature? The explanations I have heard so far are that increasing temperature increases vibrations in the lattice structure resulting in the number of ...
0
votes
0answers
53 views

Does the presence of atoms hinder current flow?

When current flows through a material, electric resistance is observed when the electrons collide with the material's vibrating atoms. My textbook says that when we cool the material till the point ...
1
vote
2answers
129 views

Total Resistance in a Tetrahedal loop [closed]

Imagine if I placed resistors of 1 ohm each in shape of tertahedal. What would the total resistance be between A and D? I can't find any website that gives me a good explaination.
-1
votes
2answers
81 views

How to convert RL Circuits? [closed]

How do we convert a parallel RL circuit into its equivalent series RL circuit ?
1
vote
1answer
3k views

Why is stainless steel a poor conductor of electricity?

I recently had a metal plate put in my shoulder and was wondering why stainless steel isn't a good conductor (At least I hope it isn't). Does the alloy just lack free electrons? Why is that?
0
votes
3answers
73 views

Capacitor related query

Why does a capacitor charge only upto the voltage of the source? I mean in an r.c. circuit if we have a resistor that is in series with the capacitor then because of the potential drop there will be ...
3
votes
4answers
619 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 ...
1
vote
1answer
119 views

Electric field and capacitance across a resistor

Using a simple lattice model of conduction, where electrons are accelerated by an electric field, and are slowed down by bumping into the lattice, you get the following equation for current density: ...
-8
votes
3answers
4k views

Why current through all the resistors in series is considered to be same? [duplicate]

Consider the circuit shown, where $R_{1} > R_{2}$. I meant to say that resistance offered by the resistor 1 is greater than the resistance offered by the resistor 2. Keep $t$ constant i,e ...
1
vote
1answer
87 views

Resistances in a circular loop

I have no idea what formula I'm supposed to use.I just want to know the concept that would allow me to get the answer. I know basic concepts of electricity like charge, currents, etc., but as far ...
0
votes
1answer
86 views

Does a battery in a vacuum produce a current?

I've always assumed that the strong resistance of air is the reason there is no flow of electrons between the terminals of a battery until a wire is connect. However, in a vacuum there is no resistive ...
10
votes
3answers
535 views

How does electricity 'decide' on it's pathway? [duplicate]

I'm struggling to understand the fundamental concepts of electricity, more specifically, the way in which it 'chooses' its optimal pathway. I appreciate electricity will always choose the path of ...
1
vote
3answers
1k views

Calculate for Multiple Resistors with a Bridge

Background A circuit is constructed with five resistors and a battery as shown. The battery voltage is V = 12 V. The values for the resistors are: R1 = 78 Ω, R2 = 150 Ω, R3 = 132 Ω, and R4 = 83 Ω. ...
-1
votes
1answer
380 views

Electric circuit question [closed]

http://www.fisme.uu.nl/nno/opgaven/bestanden/Ronde1-Theorie-2009.pdf, question 5: You have to calculate Id when the switch at S is opened, when its closed, the Id = 0.5 A. All resistors are ...
0
votes
3answers
226 views

Potentiometer voltage change

I'm trying to understand simple things about electricity reading allaboutcircuits.com web. This chapter includes image which´s principle I don't understand. Here it is: When supplying constant ...
0
votes
1answer
227 views

Effective Resistance [closed]

For the combination of the resistors, shown in the figure. Calculate the equivalent resistance between A and B, please help me to find the answer of this complicated question this is a question from ...
1
vote
2answers
2k views

why does headlights dim when a starter motor is turned on

okay first of all, what exactly does the starter motor do? does it increase the current flow and decrease voltage? and does starter motor have its own internal resistance? i understand how there is a ...
0
votes
1answer
258 views

Conductor resistance calculation method

1. What are the variables that effect on a conductor resistance (I mean all of them)? First of all I would like to say that I know how to calculate the resistance of a conductor using the method ...
0
votes
2answers
120 views

In which direction should flow of electric current be taken while solving problems?

Consider a simple circuit with a battery of $\theta\ \text V$s, and two resistors of $R_1 \ \Omega$s and $R_2\ \Omega$s connected in series. Let us assume that $R_1$ is connected nearer to the ...
6
votes
2answers
416 views

why is a resistor frequency independent

I had a doubt that why is a resistor, frequency independent? Since, as frequency increases the movement of electrons increases so heat increases which causes change in resistance. So my question is ...
0
votes
0answers
120 views

Taking length/area element when trying to find E.resistance

I am trying to find out which 'element to take' (and why), When trying to find the resistance of some material with non-uniform resistivity $\rho$. I'll give an example: Say we have a co-axial cable ...