Monday, 8 June 2015

Lab22 Electromagnetic Induction

We did several questions on activPhysics about magnetic flux and induced emf.

And the answers reveal that several rules we need to know about relations between magnetic field and induced emf. For example the angle between area and magnetic field is 90 and we get 0 emf; 

Due to the fact as we invert the current direction the force will pull invert the stick
When Prof Mason turn on the generator, the metal rod pulled in 

 


In the next activity, we look at Motional EMF and answered the questions on the whiteboard and we see some of the useful equations like flux=BvL..



We leanred about inductor is useful in circuit and deduct the equation above.

And in comparison, we find a pair match the equation of inductor which is for capacitor. The capacitance has relations with I and V and by that saying, we can use V and dI/dT to calculate capacitance and use I and dV/dt to calculate Inductance!

We plug in the definition equation for inductor into the magnetic flux equation. What happens?
We find the realtionship between emf , current and inductance! If we know the rate of current, coil area, loop count, inductance, we can calculate the emf.

Next,we use this equation we deducted previously to solve a problem.--Inductance of solenoid



We can also deduct the unit of inductance L which is khm^2/C^2, or henry




We decrease the current, what change will be for the graph?


This is the solution we find very useful during solving the activphysics question. It is a problem in which asking current, given the ratio of time divided by time constant



This is answer to RL circuit quesitons in activPhysics. We found that when an inductor is connected, we have an induced emf that is opposite of the emf from the battery supplying the current. As time increases, the inductance increases and as resistance increases the inductance decreases.  If the inductance is large, we get that the current will reach equilibrium slower than if we increase the resistance which will allow for the current to reach equilibrium faster. The relationship is confirmed in our time constant relationship with resistance.





conclusion: We have practiced our knowledge and several useful equations of the RL circuit, inductor, magnetic field and induced emf.









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