What is the resistance of a 0.2 H coil for a given time constant without prefix?

In summary, a student submitted an assignment with a question about a figure used in their answer. The question involved determining the resistance of a 0.2 H coil used to replace an inductor in a circuit with a time constant of 0.55 ms. The student's method for finding the new total resistance was correct, but there was a typo in their answer of 63.64 Ω instead of 33.64 Ω. The lecturer may have questioned the origin of the 33.64 Ω value, possibly due to a misunderstanding of the question or lack of shown work.
  • #1
ilovescience85
25
0
Good afternoon all,

I recently submitted a assignment and my lecturer has questions a figure i have put as an answer.

Question was; An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply.

Determine: the resistance of a 0.2 H coil used to replace the inductor if the circuit’s time constant falls to 0.55 ms.

I used R=L/t = 0.2/0.00055 = 363.64ohms
circuit original resistance is 330Ω so an additional 63.64Ω would be apostioned to the new coil? He has asked where the 63.64ohms has come from??

Am i right in what I've siad or have i totally misunderstood?

Any help would be great, i still passed the assignment but just want to be sure.

Thanks
 
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  • #2
Your method new total resistance look fine. But pay attention to the old resistance: was it 300 or 330 Ohms? :wink:
 
Last edited:
  • #3
Sorry my bad, it should read 33.64ohms
 
  • #4
ilovescience85 said:
Sorry my bad, it should read 33.64ohms

Ta da! :smile:
 
  • #5
Hi sorry the 33.64ohms was the answer I had put above was just a typo. Why is he questioning this figures origin?
 
  • #6
ilovescience85 said:
Hi sorry the 33.64ohms was the answer I had put above was just a typo. Why is he questioning this figures origin?

If your answer was 33.64 Ω then I don't know why he would question it, unless you didn't show your work.

The alternative is that he misunderstood the question and assumed that the 330 Ω resistor was replaced as well. Then the new coil would have to have the full resistance value of about 364 Ω.
 

FAQ: What is the resistance of a 0.2 H coil for a given time constant without prefix?

1. What is coil resistance?

Coil resistance refers to the amount of opposition that an electrical current faces when passing through a coil of wire. It is measured in Ohms and is a measure of how easily or difficultly electricity can flow through the coil.

2. How is coil resistance calculated?

Coil resistance is calculated by using Ohm's Law, which states that resistance equals voltage divided by current. This means that to calculate coil resistance, you need to know the amount of voltage applied to the coil and the resulting current that flows through it.

3. What factors affect coil resistance?

The factors that affect coil resistance include the length and thickness of the wire, the type of material the wire is made of, and the temperature of the wire. Longer and thinner wires typically have higher resistance, while thicker wires and wires made of materials with lower electrical conductivity have lower resistance. Additionally, as the temperature of the wire increases, its resistance also increases.

4. Why is coil resistance important?

Coil resistance is important because it affects the performance of electronic devices that use coils, such as motors, transformers, and speakers. Understanding the resistance of a coil can help engineers design more efficient and effective circuits.

5. How can coil resistance be measured?

Coil resistance can be measured using a multimeter, which is a tool that measures voltage, current, and resistance. To measure coil resistance, the multimeter is connected to the ends of the coil, and the resistance value is displayed on the screen. Alternatively, the resistance of a coil can also be calculated using the dimensions and material of the wire.

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