# Search results

1. ### I Reference for measuring the speed of of light

I don't know what's the appropriate title for my question but here it is: What's the reference we consider to measure the speed with respect to when we say that as the speed of a moving object approaches the speed of light the time becomes slower in the frame of this moving object.
2. ### I Resonant frequency of small particles

Hi How can find the resonant frequency of small objects like dust particles? What factors affect the resonant frequency? And is resonant frequency dependent on size? i.e. if the resonant frequency of 1 cm3 of glass is some certain value, would it be the same for a larger size?
3. ### B Work done by magnetic force

If magnetic force does not exert work on moving charges, how could a current loop immersed in a magnetic field rotate and how could a magnet attract or repel another one?
4. ### I Spooky electrons...

I watched a documentary about Quantum mechanics. There's a phenomenon which Einstien called "spooky action at a distance" states that two electrons appeared in the same event are related to each other in a spooky way,which means that if one of them has a specific state then the other one will...
5. ### Power and frequency

If I have tow sinusoidal voltage sources, one with 50Hz frequency and the other with 60Hz. which one of them will deliver more power if connected to 1 ohm resistor?
6. ### Heater resistor

if I heat a resistor, it will reach a specific temperature and keep it. because as temperature increases the resistance decreases, so reducing the power absorbed. is that true? and how to calculate how much current and voltage I have to deliver to reach a specific temperature?
7. ### A Randomness vs chaos...

The universe is random or chaotic?
8. ### Object oriented programming

I have a problem with understanding the concepts of "object oriented programming" I do not know what is an instance, object, method,interface... I have read many examples from the real world but I need a sample code with labeled instance, object, method, interface I wish the idea is clear
9. ### Synchronous motor

how is the back emf affected by the flux of the rotor? I know the relation : Ea=k*phi*w but i need a physical explanation
10. ### Transformer efficiency

hello there i have some confusion about transformer efficiency when it is max? and how it is calculated in different loading conditions e.g. at 80% of full load or at given PF
11. ### I Dual nature

Light can act like a wave or a particle ,depending on why? when two photons intersect they must collide since they are particles but rays independence tells they won't
12. ### Magnetic beakdown

In a ferromagnetic core of a transformer why could breakdown happen if we reach "over_saturation" in other words: magnetic flux could make breakdown in some material just like electric current how does that happen?
13. ### Light speed

can someone reduce the speed of light?
14. ### Capacitor and inductors

Physically, can someone explain why does not the voltage on the capcitor change immediatly? and why does not the current in the inductor also do? :smile:
15. ### Complex power

Why does a load consume reactive power? How can we produce reactive power? And what is the relationship between instantaneous power and complex power?
16. ### Electrostatic charge

Someone told me that dust can not be charged becuase it does not have chemical polarity. Is that right? Should materials have chemical polarity to be charged?
17. ### The Milky Way

How did we know that our galaxy is spiral?!
18. ### Expansion of the universe

I read in "The Theory of Everything" of Stephen Hawking that all of the galaxies are running away from ours. That made me think that the Milky Way is the center of universe, since each galaxy is running away from us(like waves on the surface of water centered at one point which is the Milky...