Resistance Definition and 1000 Threads

Hi, I've had an idea for a school physics project but I'm not sure if it will work. I want to measure the volume of water in a fixed shape container by passing an electrical current though it and monitoring how the resistance changes (with a potential divider circuit). My idea is that if I...

Hello Forum, It is well known that the electrical power dissipated (in the form of heat) by a resistor of resistance R connected to a battery of voltage V is: P_diss = (V^2)/ R or equivalently P= (I^2)*(R) Clearly the smaller the resistance R, the more the dissipated power because R is at...

When you increase the resistance of a filament bulb more work is done on the bulb which means its temperature increases. This causes the ionic lattice to vibrate with a greater amplitude (since it has more kinetic energy). The conduction electrons now encounter more collisions, hence the...

1. Homework Statement Find the equivalent resistance Homework Equations Is=I1=I2=... Vs=V1+V2+... Rs=R1+R2+... Ip=I1+I2+... Vp=V1=V2=... 1/Rp=(1/R1)+(1/R2)+... The Attempt at a Solution Sorry the picture is sideways! Is this the correct method for finding the equivalent resistance? The part...

1. Consider the group of resistors in the figure, where R1 = 12.3 and R2 = 7.95http://www.webassign.net/images/omegacap.gif. The current flowing through the 7.95[PLAIN]http://www.webassign.net/images/omegacap.gif resistor is 1.22 A. What is the voltage of the batter...

Hi everyone, I am trying to simulate a circuit containing resistors, inductors and capacitors. When i calculate the Impedance of the circuit i find it to be for example 150+100j for a frequency of 5Hz. When i run the same simulation for a frequency of 15 Hz i find it to be 162+134j. I understand...

In this clip the mythbusters are investigating projectile motion at a firing range: Using the fact that the bullet fell approximately 1 inch as it traveled 100 feet, I predicted it should travel 600 feet down the firing range before hitting the ground from a height of 36 inches. Instead, it...

Homework Statement Hi there. I have to solve this problem, and I'm having some doubts. It is desired to build an electric engine of 0.9[HP], which will be connected to 220[V]. This will be done by a Cu wire with a cross section of 1.2 [mm²]. Supposing an efficency of 90% compute how long...

How does weight affect air resistance? [i.e A heavy feather falling v.s a light one}Please be simple

1. A parachutist of mass 62 kg is falling at 55 km/h when her parachute open. She then falls 24 m in the next 2.0 seconds. Find the force of air resistance acting on the parachute during those 2.0 seconds.2. Could I just find the force of friction?3. I found out what the force would be if not...

Homework Statement two 8 ohm resistors and a battery of emf 12.0V and internal resistance of 8ohms are connected in series. Calculate the power delivered to each external resistor and then calculate the power wasted due to internal resistance. I keep coming up with the answer 18 but apparently...

I am working on my graduation design project, and I am responsible for making the power supply circuit. It is a lower power source, and acts like a current source that can supply current in the range of 30 mA to 130 mA. My power supply circuit has a source impedance of 85 ohm. Our load, a...

Does anybody understand the fundamentals of what is happening in this circuit? Tungsten welding info is all about high current... but this is a low current scenario. AC input, CDI Coil generated 20Kv (estimated) suffers voltage drop over 100mm of tungsten rod. The larger the diameter... the...

Homework Statement Why is the resistance lower in a bulb which is turned on? (Compared to when it has been off) One bulb which is off has a measured resistance of ##27.0 M\Omega## When it is on it has a measured resistance of #380.9375 \Omega## Homework Equations ##\rho (T)=\rho_o(1+\alpha...

Homework Statement Hi guys, I am trying to find the Thevein resistance of a circuit, I'm only stuck on finding Rth. Can you help? I have included a screen shot. Homework EquationsThe Attempt at a Solution Well I thought that I could combine the two bottom 1 ohms in series, the 4 and 12 in...

Homework Statement a) Find Req of the circuit b) Find the potential difference across resistance R3[/B] Homework Equations Resistors in parallel = (1/R1 + 1/R2 + 1/R3 + ...)^-1 Resistors in series = R1 + R2 + R3 + ... The Attempt at a Solution a) R3 and R4 are in parallel --> [ (1/40Ω) +...

Homework Statement Hi I am working on a study task. This is the schematic of the circuit. (all resistors are 1 k ohms.) I need to calculate the following values of resistance that will be seen between the pairs of nodes, indicated by the subscripts. REF , RCD and RAB (That is, REF refers to...

Hi, i didnt know where to put this question cos its kind of multitopic, here is why... I am working on a better way to take mechanical energy from muscles, i made a teste bench for pedalling in very different ways, including traditional(circular) pedalling, the thing is. I am measuring the power...

So Volume Flow Rate (Q) = (P2-P1)/R where R is the total resistance of the system. R is directly proportional to Length and inversely proportional to surface area, and the inherent resistance (viscosity) of the fluid. But R =nL/r^4. r^4 rather than r^2. So there has to be another factor...

We have a solid cube with some mass that we fire as a projectile at some angle. The cube is launched in such a way that two of the faces are perpendicular to the initial velocity vector. Assuming there is air resistance, would the cube change its orientation while it flies, even if the mass is...

Homework Statement Hi, I need to find the total resistance of a circuit (attached file). I'm pretty sure it's really and straight forward but I'm a chemical engineer and this is coursework so just wanted to make sure I was doing it right. Homework EquationsThe Attempt at a Solution Do I just...

1. "A car moves along a horizontal road against a resistance of 400 N. What is the greatest speed in kph that the car can reach if the engine has a maximum power of 16.0 kW?"Homework Equations : P= W/change in time P= F x v (dot product) Please help ): [/B]

Homework Statement In the physics lab the following values of a resistor have been recorded as a function of the temperature: Temperature T/°C 20 30 40 50 60 Resistance R/ 213 143 98 69 47It is said that the temperature dependence of R can be described by the following equation...

Homework Statement Two bicycle tires are set rolling with the same initial speed of 3.30m/s along a long, straight road, and the distance each travels before its speed is reduced by half is measured. One tire is inflated to a pressure of 40 psi and goes a distance of 17.3m ; the other is at 105...

Hello, I am curious why in the resistivity formula you divide the length by the area? R=P*(L/A). I cannot figure why you would not take the L*A to get volume?

I've been trying to figure out this problem for hours my whole group and most of the class is stumped. We understand that we need to relate the equations of F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg. No data is given. The answer is a V=____ equation. Even just an answer to #1 would be very helpful...

Is there a formula covering this? (not including free fall/gravity) I have the drag coefficient, velocity and every other variable I think I would need for the object in particular.

An object with a mass if falling with a force that is equal to its own weight of 25 pounds. The air resistance causes a decelerate force equal to 1/2 the velocity of the object at any time. If the object falls from rest, what is the velocity of the object after 8 seconds? I'm just confused at...

Hi guys, so I've been given a physics question which is black magic to me, so I thought i will ask you for help :) Here is the question: A pile driver hammer of mass 170kg falls freely through a distance of 6m to strike a pile of mass 410kg and drives it 75mm into the ground. The hammer does...

Hello! 1. Homework Statement http://i0.simplest-image-hosting.net/picture/uklad.jpg Homework Equations \frac{1}{R} = \frac{1}{R1} + \frac{1}{R2} R = R1 + R2 3. The Attempt at a Solution I have been trying to re-draw the schematics, but with no avail. So far I have figured out that, looking...

Homework Statement Find the value of R where RL equals 50 Ω, for maximum power transfer I= 2A, R_L=50 ohms Homework Equations R_th=V_oc/I_sc KCL,KVL,V=IR The Attempt at a Solution First, I created an open circuit including everything except R_L. Then i tried to solve for the Open Circuit...

Homework Statement A wire with cross-sectional radius 0.91 mm lying along the x-axis from x=0 to x=0http://loncapa.mines.edu/adm/jsMath/fonts/cmmi10/alpha/100/char3A.png90 m is made of an alloy that varies with its length in such a way that the resistivity is given by...

Homework Statement For the circuit shown below, find the R equivalent resistance between terminals A and B. http://puu.sh/bX1Sp/33db39d1c0.png Homework Equations parallel and series circuit definition[/B]The Attempt at a Solution I admit that I don't even know where to begin with this...

Homework Statement Neglecting air resistance, if you throw a ball straight up with a speed of 20 m/s, how far will it be moving when you catch it? Homework Equations None The Attempt at a Solution

1. A) Find the Effective resistance of a tree of resistors that bifurcates 3 times. B) Find the effective resistance of a tree of infinite resistors. (if the tree below went on to infinity) Homework Equations Ohm's Law The Attempt at a Solution I have no idea how to start this. There was no...

Hi! The question is simple, seemingly... Doubling the length of a wire, doubles the resistance of the wire... Why? There is one interesting point to it: Doubling the length of the wire also makes the ELECTRIC FIELD weaker TWO times. That automatically makes the current smaller two times...

I can't get this last problem in the chapter. I am asked to find ##I_x## in the following network: My first hunch was to apply KCL to the node above the ##2I_x## source: ##10 + 2I_x - \frac{V}{2} - 3 + I_x + \frac{V}{5} + \frac{V}{10} = 0## Where I have assumed the voltage ##V## is across...

Hello All, I am a ME student but, I'm trying to teach myself EE. I am testing out a stepper motor. Here are the specs for the motor: Rated Voltage: 5.7V Rated Current: 1A per Phase Resistance per Phase: 5.7V I am using 15 VDC and want to make sure I don't blow the motor. Using Ohm's Law...

Good afternoon all, I recently submitted a assignment and my lecturer has questions a figure i have put as an answer. Question was; An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply. Determine: the...

i am doing a research about ionized air ,and i have little question how much electrical resistance ionized air have?

Does the potential decrease when it charges(electricity) pass through a resistance? Newbie here...please help :)

Let's say that I have a stick with weight evenly distributed throughout. I attach a fan to one end of the stick, then balance it from its new centre of mass. I measure the distance from the ground to the stick then drop it. The stick tilts up towards the side generating more air resistance (fan...

Homework Statement A puck of mass m is kicked up an incline (angle θ) with initial speed vo. Friction is not present, but air resistance has a magnitude of f(v) = cv2. Solve Newtons second law for the pucks velocity as a function of t on the upward journey. How long does the journey last...

Homework Statement Find the equivalent resistance of the circuit shown below. Homework Equations R=\Sigma_{i}R_{i} 1/R=\Sigma_{i}1/R_{i} The Attempt at a Solution I'm having a lot of trouble understanding how this circuit can be simplified. All I see is a big short circuit where the...

Homework Statement The no load voltage in the voltage divider circuit is 8V. The smallest load resistor that is ever connected to the divider is 3.6 kΩ. When the divider is loaded v0 is not to drop below 7.5V. Part 2) Assume the voltage divider has been constructed from 1 W resistors. What...

Homework Statement A current-carrying ohmic metal wire has a cross-sectional area that gradually becomes smaller from one end of the wire to the other. How does the current vary along the length of the wire? Homework Equations a. It increases. b. It remains constant. c. It...

Homework Statement A projectile that is subject to quadratic air resistance is thrown vertically up with initial speed v0. (a): Write down the equation of motion for the upward motion and solve it to give v as a function of t. (b): Show that the time to reach th top of the trajectory...

I want to derive some equations for a 2-D airplane's motion, specifically when it lifts off and lands. Can someone show me where I can start and how I can use differential equations to develop equations like the speed/position of the airplane in its x and y components? Also, if anyone is...

...based on the angle. Homework Statement Figure 30-78 shows a wire that has been bent into a circular arc of radius r = 24.0 cm, centered at O. A straight wire OP can be rotated about O and makes sliding contact with the arc at P. Another straight wire OQ completes the conducting...

It's impossible for an object to have no resistance but I was wondering if theoretically such a thing was possible, shouldn't the current flow infinitely fast? But instead, no current exists at all (V=I*0=0). And if the current remains the same, how come the voltage increases as I increase...