Resistance Definition and 1000 Threads

I recently made a flashlight/ laser pointer that can charge my phone, and I was wondering as to how I could make it resistant to the rain while allowing the top to be removable to switch out the batteries and make repairs. I also plan on making it attach to my arm like a gauntlet. So how could I...

Homework Statement Homework EquationsThe Attempt at a Solution I will call the topmost node T , middle node M , bottommost left node L and bottommost right node Q . I tried to use symmetry arguments . If I connect a battery across AB , i1 flows through branch AT , i2 through AM , i3...

I placed a hot metal lid on a cool surface. When i tried to pull it up, it had a lot of resistance, i had to really try to pull it up. I could hear sounds under the lid, I'm guessing it was boiling water. What do you think could have caused this resistance?

Homework Statement A metal rod can slide on a rail without any friction in the presence of uniform magnetic field of B=1T which is perpendicular to the plane of the paper.The distance between the tracks is d=0.1m and the resistance given is R=0.1 ohm.The resistance of the rail is negligible and...

What is wrong here. If I double speed drag will be 4 times higher. The engine needs to put out approximately 4 times more power. Energy consumption will be 4 time higher for a specific time period. However if it is a fixed distance I will arrive in half the time an the energy consumption will...

Hello everyone I was hoping you could help me with something, in my analog electronics course.. In the diagram below, is displayed a circuit and its equivalent... I don't understand why the input resistance is only the parallel combination of R1 and R2?? Why doesn't Rsi contribute to the...

Hello! Why does resistance to acceleration depend on both the velocity of the object as well as the direction of the force? In circular motion, we can measure the centripetal force and centripetal acceleration, then we can calculate objects mass. Speed remains constant. But we would get the...

Homework Statement Homework Equations Equations posted in pictures attached The Attempt at a Solution I haven't attempted it yet because I am confused about something. If the-cv^2 case is for objects that hit terminal velocity at the fastest rate, why are my graphs showing that I should use...

Homework Statement decreasing the resistance increases the current if the voltage remains unchanged. Homework Equations V=IR The Attempt at a Solution The solution in the book does not count this as a true statement, but it seems true to me. Is there any reason why the statement would be false?

I was wondering about contact resistance measurment test. Why do we take such test?

Hi, we have done an experiment where we have to measure the resistance of a sample of Ge doping-p and how it changes due to a magnetic field perpendicular to the sample with a costant current. We have found that R(B) has a quadratic trend (we have fit the dates with y = a[1+b*B^2] with a and b...

I have found research from multiple sources and probably shouldn't question but I want to be clear. Inside a generator you have a fixed number of poles and a fixed number of induction coils, the particulars are not important. As a pole rotates past the "inductor" which holds the coil there...

In measuring the internal resistance of a power supply, why is a resistor with low resistance used?

Hello, I came across this line in my textbook: "Total peripheral resistance (TPR) increases diastolic pressure more than systolic pressure." I don't understand how the peripheral resistance would increase the diastolic pressure more than the systolic pressure? Could some one explain that...

Homework Statement if someone could help me with this it would be much appreciated. In physics, I used a 98Ω resistor in a series circuit and measured the current and voltage output from battery, using the current and voltage I calculated the resistance. I=0.0094A V=1 Rt=1/0.0094=106.38Ω even...

Homework Statement Homework Equations - The Attempt at a Solution I tried to break it down to: But apparently it is incorrect, can someone tell me the correct configuration? And explain too! Thanks :) (Please do not give ambiguous "hints").

Homework Statement https://imgur.com/3H3pCkD R is the resistance of each resistor, determine total resistance in the circuit. (see the image in the link above) Homework Equations R=1/R₁+1/R₂+1/R₃+... (in parralel circuit) R=R₁+R₂+R₃... (in series circuit)The Attempt at a Solution I'm...

Homework Statement Work out the total resistance of a combined circuit. https://gyazo.com/935b96ff63689e2bff852f29ea48bf90 - picture of circuit layout Homework Equations Rt=R1+R2+Rn... R=V/I 1/RT=1/R1+1/R2+1/Rn... The Attempt at a Solution RT=R1+R2 =100+150=250Ω for the resistors in series...

Homework Statement I am not sure how to calculate the resistance of the circuit and each resistor using voltage and current. I know how to work the resistance out in series and parallel but am 100% how to work it out in combined. Homework Equations R=V/I, 1/Rt=1/R1+1/R2 The Attempt at a...

Homework Statement (Is the image read-able now? ) The fig 1 shows the relationship between voltage and current when voltage is applied to a certain light bulb. Next, in fig 2, the bulb is connected in series with a 12-V battery and a 5 ohm resistor. Question : what is the amount of power...

Homework Statement If you have a 100 W bulb and a 60 W bulb connected to separate electrical outlets, which will be brighter? Which has more resistance? Explain. 2. Necessary formulas P=IV and (maybe?) I=V/R 3. The Attempt at a Solution I know for sure the 100 W bulb is brighter. However...

Homework Statement Estimate the rolling resistance force for a 75gram vehicle with axle friction coefficient of 0.2 if the wheel is 40mm diameter and the axle 2mm diameter. I am having trouble with applying the axle friction coefficient. I could not find a similar problem online. Basically...

Homework Statement Why is my calculated total resistance of the circuit higher than the resistor used in series and the theoretical total resistance? In a series circuit I used a 100Ω resistor and measured the current at 1.0v intervals from 1.0-5.0v. At 1.0v the current was 8.70mA using a 100Ω...

I was looking for any credible sources who could reveal the resistance of a normal tungsten filament bulb at room temp 20 C? I heard its cold resistance is about 9.5ohms. Is that the resistance at rtp? Thanks a lot in advance!

Hello, everyone i always had this question in mind, and also tried to look for answers on the web, but alas! i can't seem to find definite answer! i am currently making a fountainpen nib with a carbide point. the traditional material for fountainpen tipping is iridium + osmium alloy...

Homework Statement Homework EquationsThe Attempt at a Solution The original question given above has been correctly answered by me .The correct option is 2) . Thinking more about this problem made me wonder if there could be a combination of L1,L2,L3(different from that given in the...

Homework Statement Find the equivalent resistance of this circuit between points a and b https://imgur.com/a/LWcIC Homework Equations The Attempt at a Solution I am not sure how to complete this problem without any variables. I tried replacing the numbers with the variables which is what I...

Homework Statement problem in title:Homework Equations 1/Rtotal = 1/r1 + 1/r2...[/B]The Attempt at a Solution [/B] I can get it down to 4 resistors...but the one's I have circled I don't know how they behave. I just need a little kick in the right direction lol. Thank you in advance!

Homework Statement Hi Physicsforum, this is my first post so apology if I make unclear equation. I try to solve this question by pluging t0 as temp. at Valley and t as temp. at Antartitca directly as oppose to setting separate equation. I got different answer than the solution said While...

Hi there, I am new here so please don't be too hard on me yet and move this post if i placed it in the wrong forum. I am developing a little experiment game and i want the train to drive using real physics, but I am really bad at physics. So my question is is how do I calculate the friction of...

Hello! I've took a course about Electrical circuits and Networks at the university, and i found out a problem which is uploaded by my professor, and i think he made a mistake! this is the solution i think that the equivalent resistances are wrong (beside Rab), for example if you look at...

Homework Statement Part C of the following problem http://www.chegg.com/homework-help/questions-and-answers/problem-1-find-equivalent-resistance-rab-circuits-figp36-q8156743 2. Homework Equations The Attempt at a Solution Hi, to solve this problem, first i tried to ignore the two resistors...

Homework Statement I have found a differential equation that models a non-linear pendulum with air resistance, and now I have data. I've looked at the following site for guidance on how to analyse the data. It compares the motion of a damped spring, and compares it to the motion of a damped...

Students seeking “deeper” understanding of basic electricity, frequently come with one of the following misconceptions. 1. Electrons are like balls, they start with potential energy and gain kinetic energy. They deliver their energy to the far end of the wire by filling a bucket. 2...

Hi all, Sorry in advance if my questions are stupid and the answers are obvious. I can see from P=VI why a high power appliance requires more current to function. However looking at ohms law and I=V/R it’s telling me that greater resistance will lead to less current. I've always figured that...

Homework Statement An automobile battery has a terminal voltage of 12.8 V with no load. When the starting motor (which draws 90A) is running, the terminal voltage drops to 11.0 V. What is the internal resistance of the battery? Homework Equations V= EMF- Ir The Attempt at a Solution I think...

There are 2 types of temp rise measurement for electrical devices, 1)resistance type 2) thermocouple type (direct measurement) My query is 1) which method is superior and please explain me the reason. 2) Which gives higher value of measurement? Thanks in advance.

For the material used in a heater plate to generate heat for example, for a given amount of power (say 4.5 kw) does the higher resistance of the material mean it will produce a higher temperature? Or is it the other way around?

Homework Statement I need to come up with an equation that would model the motion of a non-linear pendulum with air resistance. [/B]Homework Equations Fc=mgsintheta Fdrag=(1/2)p(v^2)CA The Attempt at a Solution I started with mgsintheta-(1/2)p(v^2)CA=ma After substituting v=r*omega and...

I am comparing three brands of tires to see which one provides the lowest rolling resistance and thus give the best efficiency at low speeds. I have the information of the tires such as footprint, weight (of the tire and load), speed. How would i go about doing this ? am really stumped thanks

Homework Statement A galvanometer of coil resistance 50.0 Ω deflects full scale for a current of 3.50 mA. What series resistance should be used with this galvanometer to construct a voltmeter which deflects full scale for 35.0 V Homework Equations /Known Variables[/B] R1 + R2... + Rn = Rtotal...

I am currently using a Wheatstone bridge to determine the resistance of a NTC thermistor(Futher information about thermistor: http://www.apogeeweb.net/article/38.html) and feed the difference to the setpoint (analog potentiometer) as the error signal to a PID controller, giving me a way to...

Homework Statement What is the definition of resistance? a. Resistance is the potential difference per unit current b. Resistance is the gradient of the graph of potential difference against current c. Resistance is the voltage required for a current of 1 A d. Resistance is defined by the...

Homework Statement What is the combined resistance when the switch is closed? Homework Equations IR=V The Attempt at a Solution I found that I1=5.2A and that I2=9.1A. The answers follow suit. Now I thought that calculating the combined resistance with 60/(I1+I2) would be correct, however the...

Hello, Given an infinitely long cylinder with a specified surface heat flux, the thermal resistance of an annular region is given by, R_th = ln(r_out / r_in) / (2 pi L k). When I'm calculating the thermal resistance to the centerline, r_in = 0. Does that mean there is infinite thermal...

Homework Statement Prove the following equation: ## \Delta U=\frac {R_1R_4}{(R_1+R_4)^2}(\frac {\Delta R_1}{R_1}-\frac {\Delta R_2}{R_2}+\frac{\Delta R_3}{R_3}-\frac{\Delta R_4}{R_4})E## This is used in Wheatstone bridge Homework Equations [/B] U=RI The Attempt at a Solution This has...

Homework Statement All resistors are ## R = 10 \Omega## Homework Equations Calculate the total Resistance The Attempt at a Solution all resistors are parallel, so $$ \dfrac{1}{R_{AB}} = \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} $$ ## R_{AB} =...

Homework Statement There is a conductor with the square-shaped area. the Radii are r1 , r2 with width b and resistivity ## \rho_R##. Find the resistance R between A and B 2. Homework Equations ##I = \iint_A\vec J \cdot d \vec A## ## \vec J = \kappa \vec E ## ## \vec E = \rho \vec J## ## V =...

Homework Statement Homework Equations parallel(two shared nodes in two sides), series resistor(one shared node between 2 resistors) The Attempt at a Solution I can't identify the circuit to be parallel or series in order to get the equivalent resistance. how should I finish the question? (...

Homework Statement [/B] What is the combined resistance in this circle between A and B. Homework EquationsThe Attempt at a Solution Honestly I have no idea what to here, any explanation will be great.