Measuring tiny volumes with precision and accuracy requires a micropipet. In the biology lab, micropipets are used for preparing and loading DNA samples, microscale experiments and the preparation of many types of samples. These applications rely on good technique to reduce error. This guide explains how to choose the proper micropipet for the application and techniques to help ensure that measurements are accurate and precise.
Hans Christian Oersted (1777–1851), a Danish physicist, was performing an experiment in 1820 when he noticed that whenever an electric current from a battery was switched on or off, a nearby compass needle was deflected. Through additional experiments, Oersted was able to demonstrate the link between electricity and magnetism. The following year, English scientist Michael Faraday (1791–1867) created a device that produced “electromagnetic rotation.” This device is known as a homopolar motor since the motor requires no commutator to reverse the current.
A motor converts electrical energy to mechanical energy. The simple motor in this activity changes the electrical energy output by the battery to mechanical energy as the copper wire is set into rotational motion. Any current-carrying wire produces an associated magnetic field. The electrons in the wire are subjected to a magnetic field and experience a force—referred to as the Lorentz force—that is perpendicular to both the magnetic field and the direction of movement. At some point along the length of the wire, the electrical current is not parallel to the magnetic field. The resulting Lorentz force is tangential and induces a torque on the copper wire. This torque causes the copper wire to spin.
When charge moves, we call it electric current, but the word current is usually reserved for things like water flows. Does electric current really work like that? Electrons are quantum particles, so we have to be careful.
What’s Going On?
When a magnet is moved by a coil of wires, you can induce an electric current. This is the principle behind how most of the electricity is produced in the world; it’s just a question of where you get the energy to move the magnets. Every time a magnet passes the coil, a small amount of electricity is created, which makes the LED lights briefly flash on. Continue reading
Every dry cell can be considered as being made up of two parts. Internal Resistance cannot be separated from the cell because coulombs need energy to move through any real material (including cells). Coulombs need very little energy to move through conductors. When coulombs move through loads they need (or convert to other forms or lose) more energy. The more coulombs that move through something the more energy that is converted to other forms. Another way of saying this is; the more current flowing through something the more energy is lost.
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Armed with a large neodymium magnet, an aluminium tube and a set of scales, Andy explores the interaction of forces generated as the magnet falls and the effect these forces have on the objects’ weight.