experiment 2

Experiment 2:

Components: 1 x diode, 1 x LED

Exercise: Using a multimeter , identify the anode and cathode of the diode and the LED

	Voltage drop in forward Biased Direction.	Voltage drop in reverse biased direction
LED	1.83V	2.5V(open circuit)
Diode	0.65V	2.5V(open circuit)

Explain how you could identify the cathode without a multimeter?

Diode: There is a line on the cathode side of a common rectifier diode.

LED: Shorter side of the LED is the cathode, the taller one is anode.



Table: Data sheet of 1N4007 is as follows


Calculate first the value of the current flowing through the diode, now measure and check your answer?
Calculated: Measured:
I = Vs – voltage drop ÷ R1
I = 5 - 0 .7 ÷ 1000
I = 0.0043 Amps or 4.3 mA
Is the reading as you expected; explain why or why not?
The answer is pretty close since we got the resistance and the voltage supply and voltage drop its quiet easy to calculate and the answer is close enough.


Calculate the voltage drop across the diode, now measure and check your answer?

Calculated: 0.65 V Measure: 0.65 V
Using the data sheet
What is the maximum value of the current that can flow through the given diode?
1 Amp


For R = 1kW. What is the maximum value of Vs so that the diode operates in a safe region?


Because of the gold strip at the end of the resistor it shows +5% or -5% of the 1000v by using ohms law we got the 1000V which is V= R * I .

Max Voltage = R * I max


Vmax=1000*1


Vmax=1000 Voltes


By using the table we get the max voltage that can be put in the reverse direction before destroying the resistor.


Replace the diode by an LED & calculate the current, then measure and check your answer?

Calculated
I = Vs – VD ÷ R
I = 5 – 1.8 ÷ 1000
I = 0.0032 A or 3.2 mA


Measured
3.1 mA


What do you observe? Explain briefly


The current changes slightly due to the different voltage drop of the components. When we have the LED connected we have around 3.2 mA in the circuit but when the diode has less voltage drop then the current is a little bit higher as shown below.


I = Vs –VD ÷ R
I = 5- 0.7 ÷ 1000
I =0.0043 A or 4.3 mA

Experiment 1:

Calculating and measuring resistors:

Value (Calculating colour codes)	Measuring(Multimeter)
Brown- Black- Red- Gold 1 - 0 - * - 100 - ±5% = 1000W(1kW)	997W
Brown- Black- Brown- Gold 1 - 0 - * - 10 - ±5% = 100W	098.1W
Brown – green – Orange - Gold 1 - 5 - * - 1000 - ±5% = 10000W(10k)	9.98kW
Brown – Black – Yellow - Gold 1- 0 - * - 10000 - ±5% = 100000W(100k)	99.5kW
Orange – White – Brown - Gold 3 - 9 - * - 10 - ±5% = 390W	380.5W
Yellow – Violet – Black – Black - Brown 4 - 7 - 0 - * - 1 ±1% = 470W	467W

Choice of two resistors and their individual resistance values measured with a multimeter:

Resistor 1: 380.5 Ω Resistor 2: 98.1 Ω

Put these two resistors together in Series (end to end, one right after another) calculate and then measure their combined value

Calculated value 1 and 2 in series: 378.6 Ω

Measured value 1 and 2 in series: 482 Ω

Put these two resistors together in Parallel (connect both ends when they are side-by-side). Calculate and then measure their combined value. Show working:

Calculated value 1 and 2 in Parallel: 79.59 Ω

Measured value 1 and 2 in Parallel: 78.7 Ω

What principal of electricity have you demonstrated with this? Explain:

This principal is the Ohm’s Law:

Series: Two resistors connected in series, their combined resistance is equal to each resistance added together.

Parallel: Two resistors connected in parallel, their combined resistance is less than the smallest resistor.

Parallel

Parallel

Resistors in a parallel circuits are not calculated the same way as they are done in series. Total resistance of parallel resistors is less than the smallest resistor on the circuit . We can use this rule for a quick check to find out if we got the calculation is close to the correct resistance and for calculating the resistance we use the formulas below:

and the second formula is :

Resistors in Series

Series

The formula below is the one we use when we want to calculate the resistance of 2 or more resistors in series .

The more resistors we have in series the more resistance we have in our circuit .

Resistors

Colour code for resistors

From this chart we can calculate the resistance of a resistor ....

We also can measure their resistance with a Ohm meter or ohm setting on a multimeter.

Colour bands are calulated as the first band is 1st digit , 2nd band is the second digit, 3rd band depending on the number of bands on the resistor could be the 3rd digit if there are 5 bands or only 4 bands then it would be the multiplier... then the next one would be the tolarance percentage of the resistor .