galvanometer

Examples of galvanometer in the following topics:

• Voltmeters and Ammeters

  • Current flow through a galvanometer, IG, produces a proportional movement, or deflection, of the needle.
  • The two crucial characteristics of any galvanometer are its resistance and its current sensitivity.
  • A galvanometer can function as a voltmeter when it is connected in series with a large resistance R.
  • For other voltage ranges, other resistances are placed in series with the galvanometer.
  • Many meters allow a choice of scales, which involves switching an appropriate resistance into series with the galvanometer.

• Null Measurements

  • An unknown emfx (represented by script Ex) connected in series with a galvanometer is shown in .
  • The location of the contact point is adjusted until the galvanometer reads zero.
  • In both cases, no current passes through the galvanometer.
  • The device is called a bridge because the galvanometer forms a bridge between two branches.
  • First, it is not possible for the current through the galvanometer to be exactly zero.

• Induced EMF and Magnetic Flux

  • The galvanometer is used to detect any current induced in a separate coil on the bottom.
  • Each time the switch is opened, the galvanometer detects a current in the opposite direction.
  • Interestingly, if the switch remains closed or open for any length of time, there is no current through the galvanometer.
  • When the switch is opened and closed, the galvanometer registers currents in opposite directions.
  • No current flows through the galvanometer when the switch remains closed or open.

• Changing Magnetic Flux Produces an Electric Field

  • But when the small coil is moved in or out of the large coil (B), the magnetic flux through the large coil changes, inducing a current which is detected by the galvanometer (G).