Week 3

Week 3

1. Compare the calculated and measured equivalent resistance values between the nodes A and B for three circuit configurations given below. Choose your own resistors. (Table)

Table 1.1

Our calculated and measure values are close but they are different. This can be due to the tolerance of 5% in the resistors. 

2. Apply 5V on a 120 Ω resistor. Measure the current by putting the multimeter in series and parallel. Why are they different?
In series= 39.62 mA
In parallel = 470 mA

Yes, they are different. 
The results show that there is a huge difference between measuring current in series and measuring it in parallel. The first time the multimeter was in series which is the correct way to measure current and we got 39.62. On the other hand, when we put the multimeter in parallel, the DMM showed the circuit and it gave us a maximum current which was 470 mA.

3. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in series. Compare the measured and calculated values of voltage and current values on each resistor. 

Table 3.1

The measured values for the voltage and the current are very close to the calculated values. The current for both the resistors because they both are in the same loop because they are in a series. 

4. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in parallel. Compare the measured and calculated values of voltage and current values on each resistor. 

Table 4.1

The calculated and measured values of the current and voltage for the two resistors were close to each other. The voltage value for both resistors was the same for both the calculated and measured values because the resistors were in parallel.If the resistors were in parallels,the current value will not be the same for both resistors, for the current part, the calculated current of the 47 ohm's resistor was higher by 11.68mA and that shows there may be an error in our calculation but the calculated and measured voltage of the 120 ohm's resistors were close to each other.
5. Compare the calculated and measured values of the following current and voltage for the circuit below: (breadboard photo) 

Picture 5.1 picture of the setup for our breadboard 

a. Current on 2 kΩ resistor, 
 Calculated current across 2k resistor:1.98mA
Measured current across 2k resistor:2.03mA
b. Voltage across both 1.2 kΩ resistors.

Table 5.1

According to the table the measured voltages are pretty close to the calculated.

6. What would be the equivalent resistance value of the circuit above (between the power supply nodes)? 

The equivalent resistance of the circuit is 2.5197 kΩ

7. Measure the equivalent resistance with and without the 5 V power supply. Are they different? Why? 

yes, they are different.
The equivalent resistance without a power supply we got 2.556 K ohms which is close to the calculated value in the previous question. On the other hand, the equivalent resistance with 5 V was going up and down between 0-10 M ohms which is really large number.
the reason that they are different is because the multimeter apply a small voltage to the resistor but when 5V is applied this cause the DMM to misread the resistance's value.

8. Explain the operation of a potentiometer by measuring the resistance values between the terminals (there are 3 terminals, so there would be 3 combinations). (video) 

This video explains the operation of potentiometer,

we used 5K-ohms potentiometer. First, we measured left-middle 

terminals and the result was 5.27 k-ohms and for the middle-right

 terminal, the result was 5.39 K-ohms and across the outside( left-right) terminal

the measurement was 10.43k-ohms. The way potentiometer works is by 

dividing the resistance value between the right-middle terminal

and the left-middle terminal. The value of right-middle and

left-midle were close to each other but we think they should be the 

same value, there may be a minor error. 

9. What would be the minimum and maximum voltage that can be obtained at V1 by changing the knob position of the 5 KΩ pot? Explain.

If the knob was turned to concentrate all of the resistance to the first two terminals the Voltage at V1 will always be 0V. If the knob was turned to concentrate all of the resistance to the last two terminals the Voltage at V1 will always be 5V because that is the max Voltage supplied. 

10. How are V1 and V2 (voltages are defined with respect to ground) related and how do they change with the position of the knob of the pot? (video)

V1 will always be equal to 5 V. on the other hand, The relationship between 

voltage of V2 and different position of the knob of the pot was  

proved in the experiment. when we turned the knob of the potentiometer up, 

the voltage  of V2 increased and when  we turned the knob 

of the potentiometer down the voltage of V2 decreased .

11. For the circuit below, YOU SHOULD NOT turn down the potentiometer all the way down to reach 0 Ω. Why?

By turning the resistance all the way down to 0 all the current will rush through the potentiometer it will overload the circuit and ruin the potentiometer. 

12. For the circuit above, how are current values of 1 kΩ resistor and 5 KΩ pot related and how do they change with the position of the knob of the pot? (video). 

For the 1K resistor, the current  across it would be the same, But for the 5K pot, when the the knob is turned up the current would decrease and when the the knob is turned down the current would increase. 

13. Explain what a voltage divider is and how it works based on your experiments. 

Voltage divider is when a the voltage is being divided across different resistors in series. and it can turn large voltage values into small ones. A 5 volts was applied to the circuit, and then we used  a potentiometer which, is a voltage divider, to adjust the voltage. when we moved the knob of potentiometer all the way to the left, it decreases and when we turn it to the right it increases.
14. Explain what a current divider is and how it works based on your experiments.

A current divider is resistors connected in parallel to displace the current throughout the circuit. In the experiments we used the potentiometer to get resistance throughout the circuit to divide the current differently.