• Question: In circuits does the bigger the circuit mean that the bolb will lose light if it is very far away from the wires connecting to the battery pack

    Asked by ritchie007 to Steve on 26 Jun 2013.
    • Photo: Steven Gardner

      Steven Gardner answered on 26 Jun 2013:


      You know that when you add a resistor to a circuit with a bulb and battery that the bulb will get dimmed, right?

      Well wires have their own small resistance too. Everything has a resistance to the flow of electric current (at room temperature anyway!). A longer wire means more material that the electrons have to flow through, so more resistance that they have to overcome, so the bulb will get dimmer.

      However, if you makes the wires out of certain materials and make them really cold (we’re talking a few degrees above absolute zero, where the air would freeze solid and even helium is a liquid!), then they become a superconductor. A superconductor has no resistance, none at all! Electricity you put through it will flow forever! In fact this is what they use in the electromagnets inside an MRI machine, they cool down the wires with liquid helium and send electric current around to make a huge and very powerful electromagnet. This magnet then never needs any more power, the electricity will flow in it forever (or until the helium is removed and it warms up at least!)

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