What happens to a coil of wire as current is increased?

In summary: It is not affected by the current passing through it, unlike the EMF. In summary, the inductance in a circuit is a physical quantity that is not affected by the current passing through it. However, the EMF, which is calculated using the inductance, is affected by changes in current. In the case of an air core inductor, an increase in current would result in a proportional increase in the EMF, while the inductance remains constant.
  • #1
alexdr5398
31
1

Homework Statement


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Homework Equations


L = (N * F_b) / I (where F_b is the magnetic flux)
emf = -L * (dI/dt)

The Attempt at a Solution


I originally thought that the inductance would decrease since it is inversely proportional to current. But, looking at the equation for emf, that would also mean that emf would decrease since L is decreasing and dI/dt is constant.
 
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  • #2
alexdr5398 said:

Homework Statement


View attachment 194727

Homework Equations


L = (N * F_b) / I (where F_b is the magnetic flux)
emf = -L * (dI/dt)

The Attempt at a Solution


I originally thought that the inductance would decrease since it is inversely proportional to current. But, looking at the equation for emf, that would also mean that emf would decrease since L is decreasing and dI/dt is constant.
Your answer looks correct to me. The EMF is constant since the increase in I is linear. The inductance is a physical quantity, not affected by current (for an air core inductor). If the inductor had a ferrite or iron core, would that change your answer? :smile:
 
  • #3
alexdr5398 said:
L = (N * F_b) / I (where F_b is the magnetic flux)

I originally thought that the inductance would decrease since it is inversely proportional to current.
If the current increases, would anything else on the right side of the above equation change?
 
  • #4
berkeman said:
Your answer looks correct to me. The EMF is constant since the increase in I is linear. The inductance is a physical quantity, not affected by current (for an air core inductor). If the inductor had a ferrite or iron core, would that change your answer? :smile:

TSny said:
If the current increases, would anything else on the right side of the above equation change?

Oh, so the flux is increased by the increase in current which counters the current in the denominator?

And since inductance is a physical quantity, it can never be changed by the properties in a circuit?
 
  • #5
alexdr5398 said:
Oh, so the flux is increased by the increase in current which counters the current in the denominator?
Yes. If the current doubles, then the flux doubles. So, the formula would leave L unchanged.

And since inductance is a physical quantity, it can never be changed by the properties in a circuit?
Yes. The inductance is determined by the physical properties of the inductor (size, shape, number of wraps, type of core, etc.) as berkeman pointed out.
 
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Related to What happens to a coil of wire as current is increased?

1. What is the relationship between current and the magnetic field of a coil of wire?

As current is increased in a coil of wire, the strength of the magnetic field produced also increases. This is due to the flow of electrons through the wire, which creates a circular magnetic field around the wire.

2. How does increasing the current affect the resistance of the coil of wire?

Increasing current in a coil of wire will also increase the resistance of the wire. This is because as more electrons flow through the wire, there is increased friction and collisions between them and the wire's atoms, resulting in higher resistance.

3. What happens to the temperature of a coil of wire as current is increased?

As current is increased in a coil of wire, the temperature of the wire also increases. This is due to the Joule heating effect, where the resistance of the wire causes some of the electrical energy to be converted into heat.

4. Can increasing the current damage the coil of wire?

Yes, increasing the current beyond the wire's capacity can damage the coil. This is because the wire may overheat and melt, or the increased magnetic field may cause the wire to physically deform or break.

5. How does the length and thickness of the wire affect the relationship between current and the magnetic field?

The length and thickness of the wire can affect the strength of the magnetic field produced by the current. Longer and thinner wires will have a weaker magnetic field, while shorter and thicker wires will have a stronger magnetic field. This is due to the amount of space available for the magnetic field to form within the wire.

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