ActivPhysics 13.9: Electromagnetic Induction
For this experiment we used the ActivPhysics website to run a simulation, and then answered questions in order to analyze several factors. What we primarily analyzed here was magnetic flux and induced EMF. By answering the questions below we were able to connect the two and see their relationship based on changing values of frequency, magnetic field, and area. More detailed explanations of each analysis can be seen after the questions below.
Magnetism and Electric Current
For this demonstration, we have a large magnet with a metal rod placed between the poles. What we ended up seeing was that when a current is run through the rod, a force is created which pushes the rod outward or pulls it inward (seen below) depending on the direction of the current. This is a physical demonstration of what we have been studying, which is that when you have a current going one direction, and a magnetic field going in another, then you get a resulting force.
ActivPhysics 13.10: Motional EMF
This second ActivPhysics experiment is basically an in-depth analysis of the demonstration which Professor Mason conducted just now. The red bar seen above is our rod, and it moves based on the direction of current and magnetic field. By answering the questions below, we analyzed magnetic flux again in order to see how it changes as the rod moves. This led us to an analysis of the induced EMF in this situation and its relationship with the flux and induced current.
Self Inductance and a Solenoid
Based on the previous experiments today, and information from previous lessons, we used various equations for flux, magnetic field, inductance, and current in order to determine the new equation for inductance, which can be see as L = u(0)*n^2*A/l. This is the physical equation for induction.
Shown above is an example from the lecture in which we tested out the new, derived equation for induction. We were given a 100 turn coil with a length of 4 cm and a radius of 0.1 cm, and had to find the
inductance of that coil.
Current Flow Through an Inductor
Shown above is the calculation for the units of induction based on our physical equation for induction. What we ended up with was a kg*m^2/C^2, which is what we now call a Henry.
ActivPhysics 14.1: The RL Circuit
This final ActivPhysics activity had us analyze analyze a simple RL circuit, consisting of a resistor, battery, inductor, and a switch. We had to answer the questions above (answers are seen below), which primarily consisted of analyzing the current through the circuit while changing various factors, such as doubling the inductance and resistance. We also had to find the inductive time constant, which is the time it takes for the current in an RL circuit to reach equilibrium, and is proportional to the inductance, L, and inversely proportional to the resistance, R. The ratio of these two values is defined to be the inductive time constant, Ï„ L.
Seen below is some more elaboration on how the time constant is related to inductance and circuits, which states what was described above for inductive time constants.
Summary:
In summation, we looked at three different situations related to induction and analyzed every factor related to induction in a circuit. We looked at EMF, flux, magnetism, resistance, and inductors themselves and analyzed and calculated how they're all related and how they affect one another. The calculations done outside of the ActivPhysics demos revolved around the simulations we saw in order to gain deeper insight from them.
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