ENGR 2105 Experiment 1 – Resistor Circuits Introduction ✓ Solved

ENGR 2105 Experiment #1 – Resistor Circuits 1. Introduction

Demonstrate the voltage-current relationships in DC and AC resistor circuits. Provide experience in using Multisim Live to simulate AC and DC resistor circuits.

Theory: Ohm’s Law: V=IR • V = voltage in Volts (V) • I= current in Amperes (A) • R = resistance in Ohms. Thus Volts = Amperes x Ohms.

Analogous Example: Current in a resistor is analogous to water flow in a pipe. Voltage is analogous to pressure and opening and closing the valve is analogous to resistance.

In electronics, currents are typically in the milli-Amp (mA) or micro-Amp (μA) range. Kirchoff’s Current Law (KCL): the algebraic sum of currents through a node = zero. Kirchoff’s Voltage Law (KVL): the sum of voltages in a closed loop is zero.

Experimental Procedure: Go to and login after creating a free user account.

Measuring Current in a Single Resistor: In Multisim Live, place a 100 Ω resistor on the workbench. Place a DC Voltage source on the workbench and set the voltage to 20 Volts DC. Connect the resistor to the power supply and place a Ground and Current probe. Start the simulation, observe and record the current value.

Voltage and Current for the Three Resistors in Series: Connect three resistors in series and measure the current.

Measuring the Voltage and Current for Three Resistors in Parallel: Connect the three resistors in parallel and measure the current.

AC Voltage/Current Measurements: Use an AC Voltage source with 20 Volts and 100 Hertz. Measure Voltage and Current for each resistance.

Laboratory Area Cleanup: Wash your hands.

Writing the Laboratory Report: A formal lab report is not required.

Paper For Above Instructions

In this experiment, we aim to explore the relationships between voltage, current, and resistance in both direct current (DC) and alternating current (AC) circuits. Understanding these relationships is crucial as it forms the foundation of circuit design in various applications in engineering and technology. We will employ Multisim Live, a powerful simulation tool, allowing us to conduct experiments virtually and observe the principles of electronics without physical components.

Ohm's Law and Circuit Relationships

Ohm’s Law states that \( V = I \times R \), where \( V \) is the voltage (in volts), \( I \) is the current (in amperes), and \( R \) is the resistance (in ohms). This law establishes a direct relationship between voltage and current through a resistor, demonstrating that if the resistance is held constant, an increase in voltage will result in a proportional increase in current. For instance, if we apply a voltage of 20 volts across a resistor of 100 ohms, the resulting current would be \( I = \frac{V}{R} = \frac{20V}{100Ω} = 0.2A \).

Analogous Examples

The functioning of resistors can be visualized using the analogy of water flow in pipes. Voltage can be compared to pressure in the pipe, the current to the flow rate of the water, and resistance to the size of the valve controlling the water flow. A narrow valve represents a high resistance, resulting in lower water flow, while a wide valve signifies low resistance, permitting high flow.

Kirchoff's Laws

Kirchoff's Current Law (KCL) stipulates that the sum of currents flowing into a junction must equal the sum of currents flowing out. Conversely, Kirchoff's Voltage Law (KVL) states that the total voltage around any closed circuit must equal zero. These laws are foundational in analyzing complex circuits and ensuring conservations of charge and energy.

Procedure for DC Measurements

To perform measurements, we will start with a simple setup using a 100-ohm resistor connected to a 20-volt DC source in Multisim Live. After placing the components and wiring them correctly, we will utilize a current probe to measure the flow of electricity through the resistor.

Recording Results

The expected current for our setup can be calculated using Ohm’s Law. For instance, if our measurements yield an unexpected current reading, we can assess the components for potential errors in the arrangement or the values of the resistors used.

Series and Parallel Measurements

Next, we will assess the behavior of resistors configured in series. The total resistance in series is simply the sum of individual resistances \( R_{total} = R_1 + R_2 + R_3 \) . In our experiment, we will measure the current across a series of 100, 270, and 330-ohm resistors and verify if it matches our theoretical calculation. For parallel configurations, the total resistance can be found using the formula \( \frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} \). Understanding how current divides in parallel circuits is also essential.

AC Measurements

Switching to AC circuits, we replace the DC source with an AC voltage source (20V, 100Hz). This allows us to measure peak voltage and current, then convert these values into root mean square (RMS) values. The RMS values are crucial for comparing AC circuit behavior with their DC counterparts. This also includes taking screenshots to document our simulations, which aids in understanding design characteristics and comparison purposes.

Conclusion

This experiment encompasses both theoretical knowledge and practical application, reinforcing our understanding of resistor circuits, Ohm's Law, and the behavior of circuits in both DC and AC contexts. The activities performed not only emphasize the utility of simulation tools like Multisim Live but also cultivate a deeper appreciation for electronic principles essential for any engineering field.

References

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