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    Home / Science projects / Homemade Galvanometer
    • Homemade Galvanometer

      Homemade Galvanometer

      Galvanometers are used to detect electrical current. You can make your own using wire and a compass. Use 3-4 feet of thin insulated wire. Wrap the wire tightly several times around the compass, leaving about eight inches of wire at each end.

      Now strip about an inch of the plastic insulation off each end of the wire, leaving bare copper wire exposed. Next, press the bare ends of the wire to a C- or D-cell battery. Only leave the circuit connected for 2-3 seconds, just long enough to see the needle start spinning. The current flow will heat the battery and wires if you leave them connected for more than a few seconds.

      What happens? The current flowing through the circuit produces an electromagnetic field, which makes the magnetized compass needle try to align with it as the current moves through the circuit. If you change the direction of the current (by turning the battery around so the negative terminal will connect to the other end of the wire), then you should also be able to see a change in the direction that the compass needle moves. Try coiling your wire tighter, or make more coils around the compass. Does it make a difference in how much or how fast the compass needle moves?

      This homemade galvanometer is not a quantifiable measure of current - it shows you whether electrical current is flowing, and the direction it's flowing in, but not how many amps are being produced.

      Try testing for current from other sources. For example, stick two electrodes (copper and zinc) into half of a lemon, and then press one of the galvanometer end wires to each electrode. Is there any current flowing? Can you tell which direction it's flowing? Did the lemon battery make the compass needle move more or less than when you hooked it to a regular battery?

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    Comments




    By: NKT
    Date: Apr 29, 2016

    Hi Angora,
    Yes, just float the (iron or steel - make sure it is magnetic) needle on water - carefully with a fork so it sits on the surface tension, or float it on a bit of cork - so long as it can spin freely.

    Hi Sourav,
    The good news is, you’ve made an ammeter AND a voltmeter here. So, this is an ammeter, but it is uncalibrated. You can’t tell how much current is flowing through it. To turn it into a voltmeter, you need to put a really high resistance in there so it doesn’t short or alter the voltage you are measuring, but the little current that flows through your ammeter circuit can, with a bit of maths, tell you the voltage. The formula is V=IR
    Voltage = Current times Resistance

    so if you know the resistance and the current, you can figure out the voltage, or you can rearrange to work out the voltage from the current and resistance.

    The bad news is, you’ll need at least a basic voltmeter to get the device calibrated and work out the various inputs for the calculations.


    By: Angura Felix
    Date: Sep 05, 2015

    please can’t I use a needle to act as a compass


    By: Sourav Mukherjee
    Date: May 06, 2014

    can u please tell me how to make Voltmeter?
    : I hv a suggestion, is this possible?
      If i take a round magnet, and within it if i place a solinoid. horizontally wounded…
    two ends of wire of solinoid coming out of it; if i connect it paralally is it possible to have deflection!
    please reply.