The bulb of bicycle run with a dynamo glow brightly when speed of bicycle is increased and become dim when the speed is decreased? Give reasons
Answers
When you pass a conductor (wire) through a magnetic field, the field induces a current in the wire proportional to the rate at which the wire passes through the magnetic field. The voltage across the two ends of the wire is also proportional to the speed at which the wire passes through the magnetic field. The amount of power is the product of the voltage and current. That’s what is delivered to the bulb when it is connected to either end of the wire to form a circuit. The bulb has a fixed resistance to the flow of current. The higher the voltage the more current flows through the bulb. If the wire passes through the magnetic field too slowly there will not be enough voltage to overcome the resistance in the bulb and therefore not enough power to make the filament glow. Of course the speed at which the wire passes through the magnetic field is tied to the speed of the bicycle. Slow bike, dim light. Fast bike, bright light.
Remember that a generator is different from a battery. The generator transforms kinetic energy, the energy of motion, into an electric current. Batteries use chemical energy to create an electric current. Therefore the battery will deliver the same amount of power to the light bulb regardless of how fast the bike is going. The downside of the battery is that it produces current only as long as it can sustain the chemical reactions that supply the power. Over time the battery looses power and must be replaced or recharged. The generator requires that you the cyclist stop for a snack.