Signs of emf inducted and autoinducted

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In summary, the signs of the induced emf and self-inductance in the equation of the circuit depend on the direction of the current and can be either opposite or the same. They will be opposite when the current is increasing and the equation is k-L*dI/dt=RI, and they will be the same when the current is decreasing and the equation is -k+L*dI/dt=RI.
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bznm
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Homework Statement


I'm a little confused.. When I write the equation of the circuit, do I have to keep the signs of the induced emf and self-inductance opposite?

I'll try to explain better my doubt:
Consider a coil that has resistance R and inductance L. Running a current will give rise to both an induced emf and self-inductance, and the situation is:

induced emf= -k

self-inductance= [itex]-L \frac{dI}{dt}[/itex]

Now, my question is: the equation of the circuit is given by:

[itex]-k -L \frac{dI}{dt}=RI[/itex]

or by

[itex]k -L \frac{dI}{dt}=RI[/itex] ?

The Attempt at a Solution


I think that the self-inducted emf fights the inducted emf so, self-inducted emf and inducted emf have ho have different signs and so the equation of the circuit is given by
[itex]k -L \frac{dI}{dt}=RI[/itex]. But I'm not sure. Could you help me?
 
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  • #2


Hi there,

Great question! The signs of the induced emf and self-inductance do not necessarily have to be opposite in the equation of the circuit. It depends on the direction of the current and the orientation of the coil.

In general, the induced emf and self-inductance will have opposite signs when the current is increasing, and they will have the same sign when the current is decreasing. This is because the induced emf is always trying to oppose the change in current, while the self-inductance depends on the direction of the current.

So, in your equation, if the current is increasing (dI/dt is positive), then the induced emf (-k) and self-inductance (-L*dI/dt) will have opposite signs and the equation will be k-L*dI/dt=RI. However, if the current is decreasing (dI/dt is negative), then the induced emf (-k) and self-inductance (-L*dI/dt) will have the same sign and the equation will be -k+L*dI/dt=RI.

I hope this helps clarify your doubt. Let me know if you have any further questions. Keep up the good work!
 

What is EMF induction?

Electromagnetic induction is the process of generating an electric current in a conductor by exposing it to a changing magnetic field.

What are some common signs of EMF induction?

Some signs of EMF induction include interference with electronic devices, a buzzing or humming sound in audio equipment, and flickering or dimming of lights.

What is autoinduction?

Autoinduction, also known as self-induction, is the process in which a changing current in a circuit creates a magnetic field that induces a voltage in the same circuit.

How can I measure EMF induction and autoinduction?

EMF induction and autoinduction can be measured using a variety of tools such as EMF meters, oscilloscopes, and multimeters.

What are some ways to reduce the effects of EMF induction and autoinduction?

To reduce the effects of EMF induction and autoinduction, one can use shielding materials, reposition electronic devices, or add filters to electrical circuits.

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