Power Definition and 998 Threads

Hello, back in the day motor-generator sets were far more frequent before the advent of high power semiconductors etc. So they were used for many applications where a variable frequency high power was necessary or a purely DC output was needed. There were even some special generators that could...

To determine the voltage I did voltage/number of globes: 24/16 = 1.5V per globe - Not sure if this is correct or not To determine current, I figured out using resistance formulas that the resistance for each set of 8 globes is 15 ohms R = V/I 24/3.2 = 7.5 ohms total resistance 7.5-1 = 2 * 15-1...

Lets assume I have a telescope with an aperture of 200 mm, if we also assume λ has a wavelength of 500 nm According to; http://labman.phys.utk.edu/phys222core/modules/m9/resolving_power.htm θ = 1.22 λ/d, where θmin is the angular separation that can be resolved. 1.22 * 500 nm / 200 mm = 3.05...

I have read one shouldn't plug a power strip into another power strip. Why might that be? I don't mean to exceed the number of outlets of the first strip. I just don't have enough space between outlets to plug everything in. Like a 1/2" between the outlets would be fine.

Hi there, if a dielectric (capacitor) is described with a constant permittivit eps (or C) and loss-tangent DF, how much energy ist lost when charging the capacitor by 1V? For example: C=1, DF=0.1. When charging from 0 to 1V, the lost energy (in J) is ...? When charging from 1V to 2V, the lost...

Its unclear to me what exactly these tests entailed and how much today is still top secret. They involved inertial confinement fusion with x-rays from a fission explosion. never see this discussed - forgetting about political issues with fission, how feasible is a fusion reactor utilizing...

So the formula for power is Power = work / time. There's two types of energy transfers: heat and work. How do you calculate the power of something using heat energy in BTU/hr when BTU isn't work?

Yesterday the batteries died on my key fob and I didn't have the appropriate batteries to replace them. I thought I could use my power supply to operate the key fob to open the car door but it did not work. I thought that it may be caused by a noisy power supply at the higher frequency range of...

We use the 10 as a base for numbers because we have 10 fingers, right? The 10 commandments, awesome... we have the system of numbers to the power of 2 which makes much more sense to me. Of course feel free to pack them together to octs or hex numbers but wouldn't you say that decimals doesn't...

a) Output voltage = 2 x 6 = 12 V Current in R = 12 V / 13.5 kΩ = 8.9 x 10-4 A That is the correct answer based on the solution but I don't understand why when calculating the current in R, the resistance of secondary coil is not considered. I thought it should be like this: Current in R = 12...

The current in transmission cables = 20 MW / 240 kV = 250 / 3 A Power loss in cables =(250/3)2 x 20 x 103 = 139 MW , which is not possible Where is my mistake? Thanks

I have occasion to attempt to alleviate a lot of confusion on behalf of my utility (and me). Despite a well-trained search engine I can't seem to find a white paper from another utility/IEC/IEEE that tackles this question. Does anyone here have a good source?

I need to power a 350W thing inside the car. And I googled about it. What I learned was that there was a 100W fuse inside car lighter jacks so you can't run a 350W inverter. So I have some questions. 1. If you remove the 100W fuse and put a 400W fuse. Can the 350W power inverter sucked up the...

Hi, I'm working on a project to see if deliveries, pick ups, or both combined are better for the environment / more energy efficient / more time efficient. For example, (a) everyone collecting from a farm by bike, (b) vans bringing to supermarkets and then people collecting from supermarkets, or...

So...I have a home spin bike which unfortunately lacks the sensors of some of the more expensive models. What I'm trying to do is work out if I can dynamically calculate my power output. The spin bike itself has: - An 18kg flywheel of radius 30cm - Direct drive between the crank and the...

Particle X of mass 2 kg , and particle Y of mass m kg are attached to the ends of a light inextensible string of length 4.8m. The string passes over a fixed smooth pulley and hangs vertically either side of the pulley. Particle X is held at ground level, 3m below the pulley. Particle X is...

A car of mass 1200 kg accelerates up a hill inclined at 10 degree to the horizontal. The car has initial speed of 10 m/ s and final speed of 12 m/s after 60 s. Air resistance and friction may be ignored. Find the average power generated by the engine. The and in the textbook is 36000 W, iam...

Old style electrical panels protected residential circuits with fuses which tripped (and were destroyed) when the internal wire got too hot and melted. What is it exactly that causes a modern residential circuit breaker to trip? They are rated by amps, but heat correlates to power (volts x...

I am sure axial are used in wind turbines so i will use it as my example. Say you are using the wind turbine to generate power but its getting to windy and you want to slow down the turbine to bring it to a stop. What i want to know is ... If you can cut off the power that's been generated...

@anorlunda suggested I start a new thread about this: See: https://www.physicsforums.com/threads/grim-day-on-the-texas-power-grid.999764/post-6521013

A golf ball of mass 45.9g is hit from a tee with speed 180km/ h. The ball rises to a height of 20m having traveled along a curved path of length 61.875m. At the highest point of its path the ball is traveling at 144 km/h a) Find the magnitude of the avg resistance force acting on the golf ball...

A golf ball of mass 45.9g is hit from a tee with speed 50 m/ s. The ball lands in a pond 5m lower than the tee. When the ball lands in the pond it has traveled a curved path of length 160m. The resistance acting on the ball has magnitude 0.3N a) Find the speed of the ball just before it hits the...

Ok so for a compound microscope system like the one below, Magnification power is ## MP = M_T * M_A ##. My present understanding is that ##M_T## refers to the magnification by height ratios of the object through L1, and ##M_A##, in this case, refers to the ratio of unaided and aided angles of...

A sky diver of mass 80 kg falls 1000m from rest and then opens his parachute for the remaining 2000m of his fall. Air resistance is negligible until the parachute opens. The sky diver is traveling at 5 m/ s just before he hits the ground. Find the average resistance force when the sky diver is...

I'm pretty sure the answer is overcharged by intuition. Can someone provide a reason?

The amount of power generated by a coil in a changing magnetic field is determined by the area perpendicular to the field, the field strength, and how quickly those values change over time, and is multiplied by the number of loops in the coil. But that made me wonder what would happen if one...

A football is kicked from the ground level with speed 15m/s and rises to a height of 1.45m. Assume that air resistance is negligible a) Find the speed of the ball when it is 1m above the ground Increase in GPE= loss of KE mgh=1/2mu^2-1/2mv2 10×(1.45-1)= 1/2×15^2-v^2/2 V= 14.7 m/ s But textbook...

A box slides down a smooth ramp. The height of the ramp is 20cm and the length of the ramp is 2.5m. The box starts from rest. What is the speed of the box when it reaches the bottom of the ramp? I don't understand how to solve this. Pls help

Dear colleagues, I am dealing with rope friction and the so-called Capstan equation. Situation: A rope wraps around a cylinder with a wrap angle. It depends on the input force. There are very comprehensive approaches by other colleagues, where the friction value depends on the normal force or...

A child of mass 40kg slides down a playground slide. The child starts from rest at the top of the slide, 2m above the ground. At the bottom of the slide it's slope levels off. a) Find the child's loss of GPE I got the ans 800J there is a constant resistance of 112N throughout b) find the...

A girl of mass 50 kg travels down a water slide. She starts at the top with a speed of 2 m/s and descends through a vertical height of 5m. a) Assuming that there is no resistance, find her speed when she reaches the bottom of the slide I got the ans 10.2m/ s b) the girl's actual final speed is...

A box of mass 25kg is pulled 5m across a smooth floor by rope with tension 22N. The rope is inclined at 40 degree to above the horizontal. There is a frictional force with average value 12N. The box starts from rest. Find the final speed. Iam getting the ans 1.97m/s. The textbook ans is 1.39 m/s...

There are optical crystals that can convert a small fraction of the incoming beam of light into light of different frequency. See the Wiki article, https://en.wikipedia.org/wiki/Spontaneous_parametric_down-conversion "Spontaneous parametric down-conversion (also known as SPDC, parametric...

I understand phase voltage (phase to neutral) well, but I'm still confused by what exactly the potential difference is between any 2 phases in 3 phase power. If you were to try to find the potential difference where 2 sine wave phases cross, then at that instantaneous point, the potential...

I need to calculate the power and RMS value of some equations. The problem is, I found two methods to do that and don't know which is the right method. I have few equations to find the power and RMS value, but here is one equation. $$x( t) \ =\ 7\cos\left( 20t+\frac{\pi }{2}\right),$$ Method...

I have an air condition that is 9.000 BTU and it states at the external unit that its Power is 1.2KW. However because I know that an air condition has inductive loads (motors) its power factor is not 1 so I am not sure 1.2KW is the real power consumed. I am thinking to calculate the power...

In competitive rowing, the more people in a boat, the faster it goes, but what is the ratio of additional human to speed, and what is the theoretical limit? If I could fabricate a boat where each additional person added 100kilos, 100watts of power, and 1 meter of length to the wetted surface...

I don't have an idea of where to start. I tried to do Ein = 1/2 mv^2 ------ (1/2)(1)(10)^2 ----------- 50 but i don't know where to go from here

The answer in the textbook says 0J but I am not sure what the concept behind it is. Does it have something to do with gravity?

just want check if i got this right. is there anything i can improve or add on this example i have? Cause and why. A cause could be bending or twisting of the prop shaft due to high torque. High torque causes high angle of twist and torsion. The high torque cause high shear stress...

From a previous post about the Relationship between the angular and 3D power spectra , I have got a demonstration making the link between the Angular power spectrum ##C_{\ell}## and the 3D Matter power spectrum ##P(k)## : 1) For example, I have the following demonstration, ## C_{\ell}\left(z...

Also would a passive filter add much resistance to the circuit and rob the speaker of power? Here is the 2 way lowpass filter I was thinking of. I don't need 2 of these obviously but they seem to come as a pair. https://www.amazon.com.au/dp/B07R613YSK/

How do I find a coefficent of x^9 in a power series like this:

Hi, The original problem was : for a given number k = d + n/d, where d is a divisor of another number n, how many k <= N are prime? When I looked at this problem, for k to be prime > 2, it has to be odd. This implies d and n/d can't both be even or odd. If d = 2, then d is even and n/d has...

Hi, I am reading paper that I have to give a quick presentation on. I want to calculate the average power and peak power of the laser used, a Ti:Saphire laser. I have the wavelength they are lasing at (450nm), the repetition rate 81Mhz and the pulse duration (pulse width) of 100fs. I have done...

I am ~180lbs and have been lifting weights for about 12 years straight. I have also been running 3-4 times per week for the last 8 ish years. I have recently gotten into cycling, and noticed at the gym on the Schwinn "spin" bike, I will have peaks of around 400-500 watts, but it's definitely...

Hello all, I was wondering if it would be possible to remove the diodes from a high power dc rectifier and use it as an AC power supply? Is it possible to use an inverter/converter to convert dc output to ac? thanks

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I'm confused. I have in my hand a 120VAC power cord with a standard 3 prong US plug on one end and a common IEC connector on the other (the type that plugs into a desktop computer for example). The IEC female end is labeld L, N and Earth. Hoever if I measure the voltage between the L and...