EXPERIMENT 8

Using different resistors at Rb: At Vce during the experiment the voltage didnt vary indicating low resistance high amperage, good switch. At Vbe voltage also didnt vary much from .7volts indicating good saturation. The current through the base had little change when Rb change due to cheap multimeter, but the concept is, more current flowing through the base will open up the gate wider letting the high current flow through the collector to emitter. (the red dotted line is the load line in the pic) Beta is the ratio between Ic:Ib. Beta = Ic/Ib. My RESULTS: 1- 3.1/5= .62beta 2- 5/4.37= 1.14 3- 5/1= 5 4- 104/21.7= 4.79 5- 5.1/4.5= 1.13

EXPERIMENT 7

TRANSISTORS: Using a multimeter and checking voltage drop across the base and emitter. My reading was .8volts indicating that there is low voltage being used and high current is still being generated. The voltage drop across the collector and emitter was .o6volts indicating little resistance in the boundary meaning its a good switch and well saturated. In fig13 the area coloured black is where you want your readings to be. low voltage high amps. (it is called the saturated region) The region coloured red is called the cut off region. The cut off region is where the transistor is not working properly. It is using to much voltage and also is not creating good amperage flow. (fully closed). The middle region is the active region where the transistor is working also. I learnt that using a transistor you can switch high current using low current through the base to emitter which then allows high current through from the collector to emitter to flow through.

EXPERIMENT 6

TRANSISTORS: There are two types of transistors positive (NPN) and negative (PNP) Using a multimeter in diode test mode you can determine the base emitter and collector also if its NPN or PNP. A NPN or PNP transistor is found when you get two readings on your meter with it having one leg in common. That one leg in common will decide what charge it has. If the common leg was when the red lead was touching it, it will be a NPN transistor. If it is the black lead it will be a PNP transistor. (the common leg will always be the base) To find the collector and emitter normally the highest reading of the two will indicate the emitter to base and the lower one will be collector to base. Transistors are used as a switch to use low current to switch high current. eg low current is passed through base to emitter and opens up the gate(so to speak) and lets the high current from the collector flow passed through the (gate) out to the emitter. (NPN transistor)

EXPERIMENT 5

CAPACITORS: Capacitors are voltage storage devices. They store charge until a switch is activated to discharge the capacitor. To calculated how long it takes to charge a capacitor is expressed- RxCx5=T eg 1000000ohms x .000001uF x 5= 5secs. Using an ocilliscope you can also calculate the charging time for a capacitor. Setting the ocilliscope to the correct settings 2volt per division and 250ms per division I was able to get good graph readings to calculate the charging time. I found in my results that using different sized resistors the charging time is affected. eg. it will take longer 2 charge a 330uF capacitor if you was to use a 100kohm resistor than compared to a 100ohm resistor the time will be shorter. Also changing the size of capacitor will affect the charging time because a bigger capacitor stores more voltage so it would take longer to reach full capacity. My RESULTS: #1: .ooo1Mohms x 100uF x 5 = 0.05secs #2: .00001 x 100 x 5 = .005secs #3: .00047 x 100 x 5 = .235secs #4: .0001 x 330 x 5 = .165secs. OBSERVED TIME: 1: 515ms 2: 67ms 3: 325ms 4: 1750ms

EXPERIMENT 4

SERIES CIRCUIT WITH ZENER (REVERSE BIAS) AND RECTIFIER (FORWARD BIAS): In this curcuit I had to get voltage drop readings across the resistor, zener and rectifier. The readings I took were with a Vs=10v & 15v. I found with my results they were very similar at V1 V2 V3. (across the diodes) with both Vs. These results indicate that the diodes are working fine and do not have any faults. V1 & V2 didnt change because the voltage pressure needed is 5v & .7volts. 5v is reverse bias voltage for the zener and .7v is the knee voltage for the rectifier. The one change in the results was the voltage drop across the resistor which was expected and the current flow in the circuit. These two changes both accurred as the Vs was increased.

EXPERIMENT 3

ZENER DIODES: In this experiment I placed a zener diode in reverse bias in a parallel curcuit with two 100ohm resistors. The zener diode was a 5v1 400mW. Tested twice, when Vs= 10v & 15v. I found when testing the voltage drop with the different Vs values the voltage drop was the around the same. This is because the voltage drop across a zener diode in reversa bias will always be the same no matter how much voltage is supplied because the voltage pressure required to push through in reverse bias is 5volts. When I tested it in forward bias i got a voltage drop of .86V. This reading tells us that the voltge pressure used to push through the zener to make it work is around .6V-.7V

EXPERIMENT 2

DIODES: There are many types of diodes, rectifier, zener, and L.E.D diodes. They have similar and different characteristics. One similar characteristic is that they only flow in one direction. Some different characteristics are an LED emits light, rectifing diodes only work in forward bias and is open circuit if put in reverse bias but a zener can work in both forward and reverse bias but wont short out. This is because a zener in reverse bias, when it reaches its limit stops so much voltage then lets the excess flow through in reverse bias. To test a diode you simply put your multimeter in diode test and place a lead either side of the diode. You will only get a read in one direction the other will say OL. When you get this reading you will be able to figure out which leg is the anode and which is the cathode. In a circuit diodes can be used to rectify current and or protect a certain part of the curcuit. My RESULTS: current through diode- (calculated)volts/resistance= 4.44/1000= 4mA. (measured) .4mA. Voltage drop across diode- (calculated) .7volts. the pressured needed to push through the diode. (measured) .56volts. In this experiment I learnt that the current in a circuit will differ depending on voltage supply and the voltage used on other consumers in the circuit, if the resistor is the same.

EXPERIMENT 1

RESISTORS: resistors control the flow of amps in a circuit. They are colour coated so you know what value of resistance it has. To calculate this value you can use a resistor chart to find this out by matching the colours to the numbers and using the method it says... the first two and/or 3 numbers are the numbers you write down the next one is how many zeros you multiply by and the last colour band is the tolerance it has, eg plus or minus 5% of the total calculated. To check a resistor using a multimeter you simply have it disconnected from the circuit, have the meter on the ohms scale and adjust to the correct scale eg ohms, kilo or mega and place the one lead either side of the resistor. Resistor have a different effect when in series and parallel. In a series circuit all the resistance is added up to get your total resistance value in that curcuit. However it is different to parallel curcuits. In parallel your total resistance is your lowest value resistor in the circuit. This is because electricity takes the path of less resistance and/or highest ampz flow. Series: RT= R1 + R2 +R3 Parallel: 1/RT = 1/R1 + 1/R2 + 1/R3

My RESULTS: value (colour codes) 15ohms, 100000ohms, 47ohms, 10000ohms, 1000ohms, 100ohms. value (multimeter) 15.2ohms, 99kohms, 46.8ohms, 9.95kohms,991ohms, 101.6ohms