Resistance Definition and 1000 Threads

Homework Statement Household water heaters use a 240 V rather than a 120 V source. What is the resistance of a water heater's heating element if it heats 40 gallons (151 kg) of water from 15 C to 60 C in 15 min Homework Equations P = IV P = I^2R I = dq/dt The Attempt at a Solution Honestly no...

Homework Statement Homework EquationsThe Attempt at a Solution I chose A, I understand how the resistance is the gradient, but if it is the gradient and the gradient is constant , shouldn't the resistance stay constant? (But the answer is B) Please help~thanks a lot~

Homework Statement Is the resistance equal to V/I at any point, or is it the gradient at that point? And Why? Homework EquationsThe Attempt at a Solution shouldn't it be the gradient? because it is change in V over change in I? Thanks~

i really need help about shunt and series resistances i just want to know if they are constant or variable ? if they are variable what make them increase or decrease?

Homework Statement before that, can you tell me about "current flow in this circuit" if : A. the switch is open B. the switch is closed the Question is No. 1 Calculate the resistance of R if the value of the current I in the figure is 0.50 A. ( i think it is related to no 2) no 2. Calculate...

Homework Statement A battery of 10 volts is connected to a resistance of 20 ohms through a variable resistance R.The amount of charge which has passed through the circuit in 4 minutes,if the variable resistance R is increased at the rate of 5ohms per minute is: A)120 C B)120ln2 C C)120/ln2 C...

Homework Statement In a potentiometer 99cm of wire of resistance 99ohms is connected with a battery of 50V and 1ohm internal resistance.Find emf of battery giving zero deflection for a length of 13cm. Homework Equations Sadly,the formula I know is only for ideal emfs,which states that: If two...

Homework Statement A battery of emf 2V and internal resistance 0.1ohm is being charged with a current of 5 ampere. In what direction will the current flow inside the battery?What is the potential difference between the two terminals of the battery? Homework Equations If a battery of emf E and...

Homework Statement A small generator of 5kW, 240V and a constant frequency is used to light up 35 bulbs in parallel, each one has (240 V, 60 W) printed on it. Calculate the resistance of each light bulb. Homework EquationsThe Attempt at a Solution Attempt 1[/B] Pw = V²/R ----> R = V²/Pw...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] All the resistors are connected in parallel across A and B .The equivalent resistance is 1/Req= (1/R) +(1/2R) + (1/6R) + (1/12R) + ... I tried to work with few terms and it seems the effective resistance tends to zero as...

Homework Statement The question reads: The following graph shows the relationship between voltage V and current I, through a particular electrical component. (The line in graph is straight, not showing properly in the photo) What is the electrical resistance of this component when the...

Homework Statement Prove the equation for ΔRC. (See the first attachment with the circuit schematic inside) Homework Equations (The equation for RC, in both attachments) The Attempt at a Solution You can see my attempt at a solution in the second attachment. I'm stuck at the step shown in the...

edit: The key thing I am after is why the ferrite might be responsible for the increase in resistance I measure on the coil. Hello, i have a coil designed to be 2.2mH and54 ohms. When an MN60 ferrite (T-ish core) is used with it, the inductance rises to 6.1mH as expected, and the resistance...

Homework Statement In the circuit below, the RMS of the AC source is 100V, the inductive reactance is 50 ohm, the capacitive reactance is 200 ohm, the resistance is 40 ohm and the current flows in the circuit is 0.644 A. Determine the reading of the voltmeter. Homework EquationsThe Attempt...

Hello, I'm having a question regarding the sensors and the techniques in fluid mechanics. Since my skills are amazing in this field, here I'm asking you questions xD I want to measure the air pressure of this tube/pipe (P1,P2,P3). This pipe will be flushed with water and then with compressed...

Hello, I would like to ask if I have this data from impedance spectroscopy: frequency, Z(im), Z(Real), how should I calculate conductivity ? Should I use R(im) or R(re)?

Homework Statement Find the total resistance of the circuit Homework Equations Parallel resistance: 1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ..., Series resistance: R1 + R2 + R3... The Attempt at a Solution The 1470 ohm resistor is parallel to the 50 ohm resistor and the 1000 ohm resistor, but there is...

Homework Statement 1. Use resistors of 30 ohms, 40 ohms, 50 ohms, and 50 ohms to create a circuit with a total resistance of 95 ohms. 2. Find the amount of current going through two of these resistors if the circuit is attached to a source of 12 v. 3. What would be the voltage drops for the...

How am I supposed to calculate ohmic resistance from a non-linear electronic device component? Say, for example, I need to calculate ohmic resistance of a pn junction of bipolar junction transistor from its forward I-V characteristics curves. (It can be either Base-Emitter junction or...

Homework Statement [/B]Homework Equations ##F = -kx = m\ddot{x} ## ## f = \frac{2\pi}{\omega}## ## \omega = \sqrt{\frac{k}{m}} ## ##\ddot{x} + \gamma \dot{x}+\omega_o^2x = 0 ## ##\gamma = \frac{b}{m}## The Attempt at a Solution I'm stuck on part c of this question. Using the above equations I...

Homework Statement So this problem is on Introduction to Electric Circuits 9th Edition (Richard C.Dorf) This asks me to express the gain of this circuit Vo/Vs by terms of the resistance of R. Homework Equations KCL, KVL, some ideal OP AMP characteristics... The Attempt at a Solution...

I have a lab to work through tomorrow morning and i need to be able to explain how the voltage, current and resistance in the compound circuit diagram below is distributed, and write an equation which can be used to measure the total resistance of the circuit. I know that when you normally try...

I passed small voltages (0-5V) through a known resistance, measured the current each time, and got different "effective resistances" for each case. However, when graphed, the effective resistances appear to approach the known resistance of the circuit as a limit at higher voltages. What is the...

I am creating an equations sheet for electronics forumlas and am wondering if it is OK to write the equation for resistance in parallel like this:

I'm (self)studying the physics of heat transfer at the moment. My book gives a relationship between heat transfer rate and thermal resistance as ##\phi=\frac {A \Delta T} {R}##. My book is not in English, so hopefully that is not the cause of this misunderstanding. I double checked that heat...

Homework Statement An inductor is connected in series with an AC source, the rms output voltage of it is 260V and a hot-wire ammeter reads 2A. If the ratio of the voltage across the ammeter to the voltage across the inductor is 5/12, determine the resistance of the ammeter. (Neglect the...

Homework Statement In the circuit attached below, what's the resistance between A and B? Homework EquationsThe Attempt at a Solution I'm finding it difficult to interpret this thing. Are resistors 1 and 2 in series or parallel? What does the loop above 1 and 2 actually do, in terms of how much...

Homework Statement Question from OCR A Level Physics Exam 2014 (i) and (ii) = definitions (iii) = explanation (iv) = P.d. at 6Ohm Resistor = 0.48V (v) Suggest why the p.d. between X and Z is zeroHomework Equations I don't think there are any The Attempt at a Solution I couldn't understand...

Hi, Silly little question about the transformer short circuit test. When I perform it with the secondary shorted and I get Req = Power / current2 is this Req = Rpri + Rsec? If I measured Rpri and Rsec with a multimeter? Thanks

Homework Statement Find the effective resistance between X and Y. I have attached the circuit to this post. Homework Equations V=IR The Attempt at a Solution I did 0.25+0.5+0.5=1.25 then flipped the fraction to get 0.8ohm. I considered as if two resistors are connected in series and rest are...

Hi everybody Does anyone familiar with this equation? Acceleration resistance, = {(load MOI/mech. efficiency) + (motor MOI) x rpm^2} / {3.65 x 10^5 x acceleration time} = {(kgm^2/ƞ) + (kgm^2) x rpm^2} / {3.65 x 10^5 x second} = final value unit is in kilowatt (kW) It used to calculate the...

Hello Physics Forums! My problem is as follows. I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal...

This question is purely theoretical, so don't worry about safety or doability. Is there a way of calculating how many watts it takes to heat different metals? To be specific, how many amps and bolts it would take to get lead to its melting point. Thanks in advance.

Homework Statement Two rocks are thrown off a cliff at the same initial speed, v. The first rock is launched at an angle, ϴ, directed below the horizontal. The second rock is launched above the horizontal at the same angle. If air resistance is negligible, the rocks would hit the ground at the...

Homework Statement When an external resistor of resistance R 1 = 14 Ω is connected to the terminals of a battery, a current of 6.0 A flows through the resistor. When an external resistor of resistance R2 = 64.4 Ω is connected instead, the current is 2.0 A. Calculate the emf and the internal...

Hi, The Circuit I am referring to is a simple series circuit with the resistance of the wire is negligible. I am confused about the fact that if we increase the resistance of a resistor in a circuit, the PD across the component will also increase. From my understanding I thought increasing the...

Hi, I want to measure the motor resistance of a gear DC motor by experimentation and Ohm's Law. Should I measure the current without the gear head, with the gear head, stall current (with gear head) or stall current (without gear head)? I am trying to obtain values for Equation 4 in...

What would be the theoretical relationship between/ a formula for the salt concentration in distilled water and its electrical resistance?

Homework Statement . [/B] An 11kv motor is fed by cables from a transformer via switchgrear, having a phase impedence of 0.3 + j0.3 ohm. The Earth return path to the transformer neutral has a resistance of 0.42 ohm. Determine a suitable value of neutral resistance if the voltage rise at...

Homework Statement There is a figure, I'll try my best to draw/describe. 1. All three resisters are in parallel ___R____ !___R____! !___R____ ! 2. 2 resisters are parallel and one in series, after the parallel (ignore the dots) ___R___ ... _____R___ !___R___ ! 3. 2...

I would like to know the sheet resistance of a metal mesh that consists of 3 larger busbars (W=0.0025 cm L=0.3 cm) and 10 smaller fingers (W= 0.0002 cm L= 0,16416 cm) which are all connected by a big collection bar. The thickness of the whole layer is 0.00. This collection bar has been...

Homework Statement Homework Equations / 3. The Attempt at a Solution Here is my attempt from the homework assignment. It doesn't appear that I got any points for this question and was hoping to get a little help in correcting my issues or pointed in the right direction to start over. [/B]

I'm not realising this thing.

Helo, I am in an electronic course and we just started studying diodes. I am stuck on the following problem: Place a 100 ohm resistance in series with a diode, and plot current versus voltage across the series combination. I am also given the following values for the diode: n = 1, Is =...

Hello Experts, I am a physics newbie with big ideas. I have a question. I am thinking about how to produce a zero Resistance Current. We know we can do this using super-conductors in sub zero temperature, but maybe there's another way. My assumptions (which could be wrong): 1) Resistance in a...

If we continue to draw a specific amount of power from a cell (re-chargable), how will the internal resistance of the cell vary? Is there any particular mathematical relation between them? Please help me understand

Homework Statement What is the average resistance force F acting on the satellite during its flight, m = 3000kg, h=300km. Homework EquationsThe Attempt at a Solution If it is llow orbit, so it inhibits the resistance of the atmosphere. In 300 km is no air, so no resistance ...?

If air resistance increases with velocity, then if a ball is thrown upwards, does air resistance decrease as the upward velocity of the ball decreases or does it only increase and remains constant when the upward velocity of the ball decreases?

There are two circuits, each consist of a cell and two bulbs, in one circuit they are in parallel, and in the other they are in series. What's the best way to remember which lamp has the greatest pd, current and resistance when one bulb is brighter than the other in the series and parallel circuit?

Hello, I'm a physician with special interest in cardiovascular physiology. I'm trying to comprehend the basic physics of the cardiovascular system. Here's my thought process - Simply stated - the heart muscle contracts, thereby causing a reduction in the cardiac chamber volume and release of...