Write a MATLAB script that calculates the total resistance of three resistors connected in parallel. The values of the resistors should be input by the user. Display the result with appropriate labeling.

Here are the solutions to the MATLAB questions:

1. MATLAB script for parallel resistors:

% Clear workspace and command window
clear;
clc;

% Get resistor values from the user
R1 = input('Enter the value for R1 (in Ohms): ');
R2 = input('Enter the value for R2 (in Ohms): ');
R3 = input('Enter the value for R3 (in Ohms): ');

% Calculate total resistance for parallel connection
% Formula: 1/R_total = 1/R1 + 1/R2 + 1/R3
R_total = 1 / (1/R1 + 1/R2 + 1/R3);

% Display the result
fprintf('The total resistance of the three parallel resistors is: %.2f Ohms\n', R_total);

Explanation:

• clear; clc; clears the workspace and command window for a clean start.
• input() prompts the user to enter values for $R_1$, $R_2$, and $R_3$.
• The formula for parallel resistors is used to calculate R_total.
• fprintf() displays the calculated total resistance, formatted to two decimal places, along with appropriate units.

2. MATLAB script for plotting capacitor voltage in an RC circuit:

% Clear workspace and command window
clear;
clc;

% Define given parameters
R = 1000; % Resistance in Ohms (1 kOhm)
C = 100e-6; % Capacitance in Farads (100 microFarads)
V = 5; % Supply voltage in Volts

% Define time vector from 0 to 10 seconds
t = linspace(0, 10, 500); % 500 points for a smooth plot

% Calculate voltage across the capacitor using the formula
Vc = V * (1 - exp(-t / (R * C)));

% Plot the results
plot(t, Vc, 'b-', 'LineWidth', 1.5); % 'b-' for blue line
grid on; % Add a grid to the plot
xlabel('Time (s)'); % Label for the x-axis
ylabel('Capacitor Voltage (V)'); % Label for the y-axis
title('Voltage Across Capacitor in RC Charging Circuit'); % Title of the plot
legend('Vc(t)'); % Add a legend

Explanation:

• The given values for $R$, $C$, and $V$ are defined. Note that $1 \text{k}\Omega = 1000 \Omega$ and $100 \mu\text{F} = 100 \times 10^{-6} \text{ F}$.
• linspace(0, 10, 500) creates a vector t with 500 evenly spaced points between 0 and 10 seconds.
• The formula $V_c(t) = V (1 - e^{-\frac{t}{RC}})$ is implemented. exp() calculates $e$ to the power of the argument, and . operators ensure element-wise operations for the vectors.
• plot(t, Vc) generates the 2D plot.
• grid on, xlabel, ylabel, title, and legend are used to add appropriate labels and a title to the plot for clarity.

3. MATLAB user-defined function and calling script:

a) User-defined function (power_calc.m):
Save this code in a file named power_calc.m in your MATLAB working directory.

function P = power_calc(voltage, current)
%POWER_CALC Calculates electrical power.
%   P = POWER_CALC(voltage, current) calculates the electrical power (P)
%   given the voltage (voltage) in Volts and current (current) in Amperes.

P = voltage * current; % Power formula: P = V * I

end

Explanation:

• function P = power_calc(voltage, current) defines a function named power_calc that takes two input arguments (voltage, current) and returns one output argument (P).
• P = voltage * current; calculates the power using the formula $P = V \times I$.
• end terminates the function definition.

b) Script to call the function (e.g., main_script.m):
Save this code in a separate .m file (e.g., main_script.m) in the same directory as power_calc.m.

% Clear workspace and command window
clear;
clc;

% Define voltage and current values
voltage_val = 12; % Volts
current_val = 2.5; % Amperes

% Call the user-defined function to calculate power
calculated_power = power_calc(voltage_val, current_val);

% Display the result
fprintf('Given Voltage = %.1f V and Current = %.1f A\n', voltage_val, current_val);
fprintf('The calculated electrical power is: %.2f Watts\n', calculated_power);

Explanation:

• voltage_val and current_val are defined with the specified values.
• power_calc(voltage_val, current_val) calls the user-defined function, passing the voltage and current values. The returned power is stored in calculated_power.
• fprintf() displays the input values and the calculated power with appropriate units.