Motors and Magnetic Fields 11/13

Today we learned about motors and how they work.

The first motor we were given taught us how torque is =IAxB and how and then we expanded by saying that toque is also NIAxB. therefore we would have a larger torque by using more loops. 

In this picture we have created an electromagnet. where the B vector is perpendicular to the steel plates. the cross sectional are would be the loops around the green holder and the current would be the same for both.

Here we have a DC motor being powered by a 3v battery at a steady current. with a magnetic field perpendicular to a to the current giving it a force to turn. 

Magnetic Field and Forces 11/4

Here we can see the magnetic field surrounding the bar magnet.

Here we see how the magnetic flux of a closed surface is similar to gauess law for electric flux. integral of b*dA =0

The unit for the magnetic flux is the webber.

Here we can see that the right hand rule still applies. and that force is equal to F=qVx B

A simple sample problem where we have a known magnetic field velocity and theta

A particle in a magnetic field is being affected by a magnetic force. notice how the force propels it forward. and the electric force bring it down,

A Heat Gun

This shows how in a magnetic field a particle will tend to move in a circle clockwise or counter clockwise depending on charge magnetic field and direction of velocity.

The velocity of the charge is also the current though the wire so the wire experiences a force up or down.

This explains the video we just saw that the current I through a wire some length L will experience a force if there is a perpendicular magnetic force.

all the forces around the loop cancel out.

The force on a hemisphere from a constant magnetic field can be found by splitting wire into tiny pieces of dL length. L=rtheta.

Diodes Transistors and built a Speaker 10/30

Today during lecture we went over diodes and transistors work then went on to use them in building circuits. In a diode we have an ntype and ptype junction where next to each other which then creates a depletion zone between them when a current is applied so that electrons flow from ground to ntype the diode depletion zone will disappear and if its plugged in wrong it will get bigger meaning diodes only allow current in one direction.

Here we have a breadboard circuit with an led and resistor, the led acts as a diode meaning it only allows current to flow one way.

Here we have a switch which is always in the open state,

a schematic with a transistor that will act too amplify our signal current/collector.

Osilliscopes 10/28

here we have an electron gun and we can see how moving the horizontal deflection plates and vertical deflection plates move the particle horizontal or vertical respectively.

Here we have an electronn passing through two plates a distance d apart with voltage V a distance L.
F=qE E=Vd F=qVd=ma a=qv/md and therefore we can find velocity after some time or distance.

Our work of the above problem.!

here we have a picture of our speaker connected to our function generator.

1.) sound of a sine wave output at 96 Hz.
2.) what happens to the sound when you change it to square or triangle
3.) what happens when you change the frequency.
4.) what happens when you change the amplitude

A sine wave function The y axis is measure in amps/division and the horizontal is measure in time/div

Square Wave

Capacitors in Circuits 10/23

Today we learned that a capacitor is a device that stores electric charge and electric potential energy.
We defined capacitance as the measure of the ability of a device to store charge per unit of voltage applied across the device
C=Q/V

we learned that for capacitor in series the charge is conserved and that capacitors in parallel have the same voltage drop across one another.

we also proved theoretically by using the definition of current flow and relating it to capacitance that qc= q0 e(-t/RC), and V=Vo e^(-t/rc)

Here we have applied a best fit to the graph and shown experimentally the rate at which capacitors discharge and charge. Where the constant C is equal to 1/rc.