# Lab 5 Ampere Law & Electromagnets (working with electrons) Kewei

Lab 5 Ampere Law & Electromagnets

Introduction

In this lab, we were going to use the simulation tool, which is a website www.falstad.com, to simulate some circuits and then try to build it with the same component.

Experiment 1Simulation of a charging capacitor

In experiment 1, the RC circuit is built. By switching on the switch at t=0 time, the capacitor starts to charge up. We could see the exponential curve of the voltage across the capacitor and it stablize around 10V, which is as same to the voltage supply. Also, we also observe the exponential decrease of current in this case.

Figure 1 simulation of RC circuit

Experiment 2Measuring a charging capacitor

To charge the 4.7mF capacitor (we use 220 ohm resistor), theoretically TAO would be TAO=RC=220*4.7m=1.034s. To be fully charged, we need 5 TAO, which will be 5*1.034s = 5.17s. In the following record, the scaler is 1s/block, so it’s 5s in total. Theory matches with experiment! yeah!!!!!

Figure 2 Charging the capacitor in real life

Figure 3 simulation of RL circuit

In experiment 3, the RL circuit is built. By switching on the switch at t=0 time, the voltage across the inducor starts at a very high place and decay exponentially. Consequentially, the voltage across resistor starts to increases exponentially. This can be explained easily using Lens Law, which says that inductor doesn’t allow the current to increase sharply.

Experiment 6 Make a solenoid

In experiment 6, a simple solenoid is made using wires and a power supply (this was done by Kevin and Shawn). By closing the switch or connecting the circuit, the inductor will become a big magnet and push out the coil. This function makes the device similar to a “gun”.

Figure 4 the solenoid made by Shawn and Kevin

Conclusion

In this lab, we took many inside experiment with the transient circuits, which includes RC circuit, RL circuit and solenoid. We did them both on simulations based on computer software and physical component, which is very helpful for us to get understand of the behavior of transient circuit.