EXP 17

docx

School

Northeastern University *

*We aren’t endorsed by this school

Course

1157

Subject

Electrical Engineering

Date

Jan 9, 2024

Type

docx

Pages

Uploaded by UltraSealMaster1010

Charles Williamson Experiment 17: DC Circuits The objectives of the experiment are wire up simple circuits in order to understand the relationship between currents and voltages and use this knowledge to apply Kirchhoff’s loop and junction rules. The first investigation serves to study the electromotive force of battery combinations. The sum of the two batteries in series was 3.0439 V and 1.5246 V in parallel. The second investigation introduced resistors into the circuits. The voltage of the battery was found to be 1.429 V with an internal resistance of 8.309 ohms. The third investigation featured simple resistors networks in series and in parallel. The total resistance of the resistors in series was found to be 487.2 ohms and 1079.2 ohms. Introduction Direct current (DC) circuits are a commonly utilized medium for the transfer of electrical energy. This experiment seeks to demonstrate the operation of DC circuits. The first investigation studies the electromotive force of battery combinations. The electromotive force is the voltage difference that is contained within a charged battery. The first combinations is the placement of batteries in series to demonstrate the additive properties of batteries in series. Next the batteries were placed in parallel to demonstrate the drop in voltage. Investigation 2 seeks to measure the resistance of the components in a DC circuit. The circuit was connected with resistors in order to determine the voltage of the battery under load and the internal resistance within the circuit. Investigation 3 seeks to measure the voltages and current for combinations of two resistors. The resistors were placed in series and in parallel to demonstrate the effects of these combinations on current and voltage. Investigation 1 The set up of Investigation 1 can be viewed below. An alternative set up was used to study the batteries in parallel.

Figure 1. Diagram of the 1 battery in series circuit The first objective was to determine the emf of each battery so that the experimental values could be corroborated. The emf of each battery was found using the DMM as a voltmeter. Battery 1 was 1.54 V and battery 2 was 1.50 V. The first set-up, as seen in the figure, was the batteries in series. This yielded an emf of 3.043 V. Because the emf of batteries in series is the sum of the voltages of each battery, this value is expected and within 10% of the expected value. Next, the batteries would set up in parallel. This yielded an emf of 1.54 V. Because the emf of batteries in parallel is the sum of their inverses, this value is expected and within 10% of given value. Investigation 2 Investigation 2 features the use of a resistor to measure its effects on voltage and current. The set up of the battery in series with the resistor can be viewed below. The resistance of the resistor in series was found to be 103.9 ohms. This is within 10% of the initially recorded value of 105.3 ohms. The current was found to be 0.013 amps. The voltage burden was measured to be 0.133 V. Using this value and the voltage across the ammeter, the voltage of the battery under a load was found to be 1.429 V. Using this value and the equation below, the internal resistance of the battery was found to be 8.309 ohms. Figure 2: Diagram of resistor in series with battery Investigation 3 The objective of investigation 3 was to measures the voltages and currents for combinations of two resistors. Two resistors were first set up in series with the power supply. The power supply has voltage of 5V. The voltage of each resistor was to be 1.46 V and 3.234 V for a voltage sum of 4.99V. This is within range of the observed 5 V. Next using the equation for power below, the power of each resistor was found to be 0.0043 watts and 0.009 watts. Next using the equation below, the resistance of each resistor was found and compared to the given resistance values. The experimental values were 487.2 ohms and

1079.2 ohms compared to the given values of 470 and 1000 ohms. The experimental values agree with the rule of addiction of resistors in series. Next, the resistors were set up in parallel again with the power supply set to 5V. The total current was found to be 0.002997 amps. The total voltage was 4.98V. Using these values and the equation above for resistance, the total resistance was found to be 1661.8 ohms. This value is within range of the expected value. Figure 3: Diagram of 2 resistors in series Conclusion The experiment’s objective was to understand the mechanisms within voltage, current, and resistance across DC circuits through three alternative investigations. The first investigation studied how voltage across two batteries in series and in parallel were different. Both measured values were within range of the theoretical values. Investigation two studied the resistance in order to calculate the internal resistance of a circuit. The last investigation studied the mechanisms of resistors in series and in parallel. These observed values were compared to theoretical values and found to be within range. Questions 1. The terminal voltages would be the summation or difference between the voltages. 2. The total resistance will be larger for resistors in series because these resistances are additive and while in parallel are inverses. 3. A 1.5V battery does have internal resistance. The total resistance would be 7.5 ohms and it can be inferred that this is also the internal resistance. 4. Based on the formula for R=V^2/P, the resistance would be equal to 8.07 ohms 5. The resistance between resistors in parallel is 1/2R while the resistance between two resistors in series is 2R.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version