The effects of back emf on circuit current, Physics

The effects of back emf on circuit current:

In proving the time constant, it was stated that, at the instant the switch is closed, the current (I) is zero.  This is because, at that instant in time the current in the coil and the flux surrounding the coil are both changing at their maximum rate.  This rate of change of flux produces maximum back emf, the value being equal and opposite to the applied voltage.  Therefore, with no potential difference across the circuit, no current can flow.  This fact is quite simple to prove using the equation for the self induced emf in a coil and elements of the 'proof of time constant' above:

          E  =  -L x dl/dt

The  current starts from zero, and would rise to its maximum value in 1 time constant if the initial rate of change could be maintained.

The rate of change of current is therefore given by the gradient of line AB.  The gradient of AB = BC/AC = Imax-0/Time constant.  

IMAX can be calculated using Vsupply/R, because when the current reaches its maximum value it is no longer producing a changing flux and therefore not producing a back-emf.  At this time, the whole supply voltage is dropped across the resistor. 

 

Posted Date: 9/13/2012 6:30:51 AM | Location : United States







Related Discussions:- The effects of back emf on circuit current, Assignment Help, Ask Question on The effects of back emf on circuit current, Get Answer, Expert's Help, The effects of back emf on circuit current Discussions

Write discussion on The effects of back emf on circuit current
Your posts are moderated
Related Questions
Q. The block of mass M descend with acceleration a and mass of string is m. find tension in string? Ans: The tension in the string will not be same at all points as the string h

As a longitudinal wave moves through a medium, the particles of the medium: a) vibrate in a path parallel to the path of the wave b) vibrate in a path perpendicular to the p

Q. A neutral Ping Pong ball dangles from the ceiling by a thread. A person chafes a rubber rod with animal fur and then touches the Ping Pong ball with the rubber rod. Afterwar

an object has moved through a distance.can it have zero displacement?if yes support your answer with an example

describe the construction and working of michelson interformeter?

Bohr magneton (N. Bohr) It is the quantum of magnetic moment. Bohr radius (N. Bohr) It is the distance corresponding to the mean distance of an electron through the nuc

Can CPH Theory explain the physical conservation laws? Answer; sure, all the physical conservation laws come up of properties of CPH. Everything is made of a CPH. A CPH has sta

State and explain laws of transverse vibrations in stretched strings. Describe how do you verify them using sonometer.

What is Heat? We now have several scales for measuring temperature, but first let's ask, “Is temperature the same as heat?” If I add heat to a pot of water, the water's temperatu

Explain about the monochromaticity of laser. Monochromaticity: The light emitted through a laser is monochromatic, that is this is of one wavelength (colour). Although in ca