Current in a solenoid (conceptual)

In summary, the conversation discusses the behavior of current in a solenoid compared to a regular resistor. It is explained that the current in the solenoid takes time to reach its maximum value due to the complex equations involving time and inductance. This is because the current creates a magnetic field, which induces an opposing emf that delays the rise of current. This phenomenon is known as Lenz's law and can be observed by plotting the current over time.
  • #1
Ally Doh
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Homework Statement



There is a simple set up with a cylindrical solenoid that is connected to a battery. Suppose the solenoid has a total resistance of 0.2 ohms. If the battery were attached to a regular resistor of R=0.2 ohms instead of a solenoid, the current in the circuit would immediately achieve its maximum value the moment the switch is closed. By contrast, when the solenoid is connected to the battery, the current takes time to reach its maximum value. Explain in words why the current in the solenoid takes significant time to reach its final value.

Homework Equations



I=V/R

i(t) = Vb/R (1-e^(-t/(L/R)))

The Attempt at a Solution


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I understand these two equations completely: the first one is the equation for current with a regular resister, whereas the second is the equation for current with a solenoid. Due to these equations the current through a solenoid is much more complicated to compute and doesn't only depend on the voltage and resistance like a regular resistor, but it also depends on time and inductance.
I wrote this down, but I wasn't given credit since I just basically talked about the equations, which I understand. I've wrestled with this for a while now and I guess I can't seem to understand how I would explain why the current in the solenoid takes a significant time to reach its final value.
I know that when the current goes through the solenoid it creates a magnetic field, which does not happen with a regular resistor. Is this magnetic field relating to time somehow?

Thank you in advance! I'm really interested in how this happens and I can't seem to find this information out with the resources I've looked at.
 
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  • #2
Ally Doh said:
I understand these two equations completely: the first one is the equation for current with a regular resister, whereas the second is the equation for current with a solenoid. Due to these equations the current through a solenoid is much more complicated to compute and doesn't only depend on the voltage and resistance like a regular resistor, but it also depends on time and inductance.
I wrote this down, but I wasn't given credit since I just basically talked about the equations, which I understand. I've wrestled with this for a while now and I guess I can't seem to understand how I would explain why the current in the solenoid takes a significant time to reach its final value.
I know that when the current goes through the solenoid it creates a magnetic field, which does not happen with a regular resistor. Is this magnetic field relating to time somehow?

For the behavior of current in a solenoid (which is an inductor) you must think in terms of the magnetic field produced by a current in the form of a coil.
the flux of the magnetic field produced is such that its rate of change produces an induced emf in the coil which opposes the cause that is the voltage being put on by the battery for sending the current.
this effect is known as Lenze's law.
This effect is only during the interval as the current rises from zero to its peak value as during this period the current is changing leading to change in magnetic field(flux lines)- as the current becomes steady the induced e.m.f opposite to the impressed voltage will become zero. therefore if one plots the rise of current there will be a curve which is represented by your equation.
you can estimate this time delay by actually plotting the current with time-or consult your textbook on growth of current in an inductor circuit.
 

Related to Current in a solenoid (conceptual)

1. What is a solenoid?

A solenoid is a coil of wire that is used to create a magnetic field when an electric current passes through it.

2. How is current produced in a solenoid?

Current is produced in a solenoid when an electric current is passed through the coil of wire. This causes a magnetic field to be generated around the solenoid.

3. What is the direction of current in a solenoid?

The direction of current in a solenoid is determined by the direction of the electric current passing through the coil of wire. It follows the right-hand rule, where the thumb points in the direction of the current and the fingers curl in the direction of the magnetic field.

4. How does current in a solenoid affect its magnetic field?

The strength of the magnetic field produced by a solenoid is directly proportional to the amount of current passing through it. Increasing the current will result in a stronger magnetic field, while decreasing the current will result in a weaker magnetic field.

5. What factors affect the current in a solenoid?

The current in a solenoid is affected by several factors, including the number of turns in the coil, the strength of the electric current, and the presence of a ferromagnetic core inside the solenoid. These factors can all affect the strength and direction of the magnetic field produced by the solenoid.

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