Question

For this station, you have two coils of wire (each with different numbers of loops), a magnet, some connecting wires, and a galvanometer. A galvanometer is an ammeter that measures very small currents (micro-amperes) and indicates the direction of that current. Understanding how the meter behaves is important here, because you’re going to use the meter to determine/measure current—including its direction. For this galvanometer, when (conventional) current enters the terminal on the right (as viewed when reading the dial), the needle will swing to the right. If the current flows into the terminal on the left, then the needle will swing to the left. (So the positive and negative signs on the dial simply distinguish between two directions, not the sign of the charge flowing into or out of the respective terminals.) Experiment 1a: Using the alligator clip wires, attach the coil with more loops to the galvanometer. Look carefully at the direction that the wires are turned. The idea here is that you will be moving the pole of a magnet closer to the coil— increasing the magnetic field strength in the vicinity of the coil, which is one way to increase magnetic flux. Thinking about the orientation of your loops of wire, and using the appropriate right-hand rule(s), decide which direction the current will be created in the wire as you move the north pole of your magnet towards, and into the center of, the coil—and therefore which direction the needle of the galvanometer will move. Draw a diagram below and the direction of the induced current in the wire coil as the magnet is moved as shown.

Question:Based on the above, explain briefly the principle behind an electric generator?

Answer 1

When a conductor moves in a magnetic field, an emf is induced across the conductor. This 1s the only basis on which each and every rotating electric generator works (such as portable generators) According to Faraday's law of electromagneti nduction, when a conductor links with a changing flux, it will have an induced emf across t. The value of induced emf across the conductor depends on the rate of change of flux linkage with the conductor. The direction of the induced emf in the conductor can be determined by Fleming's Right Hand Rule. This rule says that on your right hand if you stretch your thumb, first finger and second finger perpendicular to each other, and if you align your right-hand thumb along the direction of motion of the conductor in the magnetic field, and first finger along the direction of magnetic field, then you second finger indicates the direction of emf in the conductor.

Fleming' s Right Hand Rule Direction of force Current Direction of field Direction of current Now we will show you how does electricity get produced when we rotate single loop of a conductor in a magnetic field. During rotation, when one side of the loop comes in front of the magnetic north pole, the instantaneous motion of the conductor will be upward hence according to Fleming's Right Hand Rule the induced emf will have inward direction

Motion of Conductor eld emf At the same time, another side of the loop comes in front of the magnetic south pole, the instantaneous motion of the conductor will be downward hence according to Fleming's Right Hand Rule the induced emf will have outward direction

Let us connect slip ring with both ends of the loop. We can connect a load with the loop through the brushes rest on the slip rings as shown. In this case, the alternating electricity produced in the loop comes the load. This is an AC electric generator. We can also collect the electricity produced in the rotating loop through commutator and brush arrangement as shown in the animated picture below. In this case, the electricity produced in the loop (here the rotating loop of the single loop generator can also be referred as the armature) gets rectified through the commutator and the d gets a DC power. This is the most basic conceptual model of a DC generator