What is the full-scale voltage of a meter movement that has a full-scale current of 500-uA and an internal resistance of 400 ohms?

Expert Answers

An illustration of the letter 'A' in a speech bubbles

An ammeter measures currents by passing this the current to be measured through a mobile coil, and thus creating a proportional magnetic field. This field, in turn interacts with a second magnetic field created by a permanent magnet leading to a deflection of the indicator (mobile coil) proportional to the current passing through it. Because aways a coil has a resistance, there will be a voltage drop U onto this. The Ohm law states the relation between the current passing through the mobile coil  I and its internal resistance R.

`I = U/R`

Therefore the full scale voltage using the problem data is

`U = I*R =500*10^-6 *400 = 0.2 "Volt"`

Approved by eNotes Editorial Team

We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

  • 30,000+ book summaries
  • 20% study tools discount
  • Ad-free content
  • PDF downloads
  • 300,000+ answers
  • 5-star customer support
Start your 48-Hour Free Trial