INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

How to determine current in a DC motor?

How to determine current in a DC motor?

(OP)
Hi, I am having difficulty trying to figure out current and resistance in a simple DC half motor I made. Any help would be greatly appreciated. I built a half motor which consists of a coil with 10 loops made out of 20 gauge magnet copper wire . The coil sits inside 2 paper clips that are connected directly to a d cell battery. One paper clip is on the positive side of the battery and the other paper clip is on the negative side. The coil only conducts half of the time as I only sanded the bottom half of each lead of the coil. I tried to figure out the current draw by the motor by calculating the resistance of the coil and then using ohms law. The 10 loop coil is 5 feet in length. I looked at an online chart and saw that 20 gauge copper wire is 10.13 ohms/1000 ft at 20 degrees C. From this I calculated my 5 ft coil to be .051 ohms as follows.

10.13 ohms divided by 1000 ft = X divided by 5 ft
therefore X = .05 ohms

Next I used ohms law V=IR to calculate the current draw.

1.5V = I(.05 ohms)
I = 29.4a

I felt that this answer of 29.4a is wrong because I did not feel a D battery could supply that much current. When I test my motor with a digital multimeter, I get 3a when the motor is spinning and .5a when I hold the coil from spinning with the sanded coil leads conducting. What I would like to know is what is the correct way of determining the current draw for this type of motor and how is ohms law (V=IR) used. Thank you.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close