Demystifying Voltage: A Conceptual Explanation For Beginners

What is Voltage?

Voltage is defined as the difference in electric potential between two points in a circuit. It measures the “push” or pressure driving electrons through a circuit. Voltage plays a vital role in electronics by powering components and overcoming resistance in circuits.

More specifically, voltage refers to the potential energy per unit charge available to do work on a load. It can be thought of as the “pressure” in an electrical system that causes current to flow. Just like higher water pressure enables more water to flow, higher electrical pressure (voltage) enables more current to flow.

Voltage is measured in units called volts. Related units include millivolts (one thousandth of a volt) and kilovolts (one thousand volts). A common symbol used to represent voltage is V.

Table of Contents

Voltage and Current Relationship

Voltage and current are directly proportional as described by Ohm’s law. Ohm’s law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points. Introducing the constant of proportionality, resistance (R), the relationship becomes:

V = IR

Where V is voltage measured in volts, I is current measured in amps, and R is resistance measured in ohms. This means, for example, that doubling the voltage while keeping resistance the same will double the current flow.


voltage = 10 # Volts
resistance = 50 # Ohms 

current = voltage / resistance 

print(current) # Prints 0.2 amps

The above code example calculates current using a known voltage and resistance based on Ohm’s law. This demonstrates the underlying relationship driving electronics behavior.

Voltage Polarity

Voltage polarity refers to the directional orientation of a voltage source. Positive voltage corresponds to high potential relative to ground, while negative voltage corresponds to low potential relative to ground.

By convention, current is said to flow from positive to negative polarity. So in a circuit with +5V and ground, conventional current flows from +5V towards ground.

  
power = 5 # +5 Volt power supply
ground = 0 # Zero volt reference

if power > ground:
   print("+5V is positive polarity voltage")
else:
   print("+5V is negative polarity voltage")

This code example checks the polarity of a +5V power supply voltage by comparing it against ground. As expected, it prints that +5V is positive polarity.

AC Voltage vs DC Voltage

There are two general categories of voltage: alternating current (AC) and direct current (DC). AC voltage periodically reverses direction, whereas DC maintains a constant polarity.

AC is like an oscillating wave fluctuating between positive and negative. DC is fixed at one value like a steady slope. Electronic devices can utilize both types. AT voltage usually comes from wall outlets and is used when components need power exchange. DC comes from batteries and efficiently transports continuous power in one direction.


import numpy as np
import matplotlib.pyplot as plt

# AC Waveform
time_points = np.arange(0, 0.1, 0.001)
ac_voltage = 120 * np.sin(2 * np.pi * 60 * time_points) 

# DC Waveform
dc_voltage = np.ones_like(time_points) * 120

plt.subplot(1, 2, 1) 
plt.title("AC Voltage")
plt.plot(time_points, ac_voltage)

plt.subplot(1, 2, 2)
plt.title("DC Voltage") 
plt.plot(time_points, dc_voltage)
plt.tight_layout()
plt.show()

Here a simulation is coded to compare an AC sine waveform against a steady DC voltage using NumPy and Matplotlib. This illustrates their distinct yet complementary characteristics.

Measuring Voltages

Voltages are measured using either a voltmeter or a multimeter set to the volt unit. These devices measure the potential difference between two test points in a powered circuit.

To measure voltage, first ensure the circuit is unpowered. Then connect the multimeter leads across the points where voltage needs to be measured. Power up the circuit and observe the voltage reading on the multimeter display. Care should be taken to avoid short circuits.


import random

voltage = round(random.uniform(1, 12), 2) # Simulated voltage

print(f"Connecting multimeter to circuit...")

measured_voltage = voltage # Simulate measurement 

print(f"The measured voltage is {measured_voltage} volts")

This code example simulates connecting a multimeter to measure a random voltage generated in a circuit. The measured value matches the actual voltage, demonstrating basic usage of a voltmeter.

Voltage Dividers

A voltage divider is a simple circuit that converts higher ‘input’ voltage into lower ‘output’ voltage. It utilizes a pair of resistors to generate an intermediate voltage by tapping into the divider point.

The output voltage Vout is proportional to the input Vs based on the resistor ratio relationship:

Vout = Vin * (R2/(R1+R2))

Where R1 is the upper resistor value and R2 is the lower resistor value in ohms. This allows high voltages to be reduced to safe low voltages.

 
vin = 16 # Volts 

r1 = 100000 # Ohms
r2 = 10000 # Ohms  

vout = vin * (r2/(r1+r2))

print(f"{vin}V input converted to {vout}V output")

Here a simple voltage divider circuit is coded that converts 16V to 1.6V based on the resistor ratio to demonstrate the voltage dividing functionality.

Voltage Regulation

Voltage regulation refers to maintaining constant voltage levels despite changes in load current draw or input voltage fluctuations. This ensures stable operation of electronics.

Common voltage regulation techniques include linear regulator chips, switching regulators, and voltage reference ICs. Linear regulators use a resistive element to burn off excess voltage. Switching types efficiently switch to maintain target output.

 
vin = 12 # Volts  

vout = 5 # Target 5V output 

error = vin - vout

if abs(error) > 2:
   correction = error / 2  
   vin = vin - correction
   
print(f"Regulated output: {vin}V")

This code implements a simple linear regulator by calculating error compared to target and proportionally adjusting the input to maintain a steady 5V output.

Practical Applications

Voltage is applied in electrical devices and systems to deliver power, enable functionality, or transmit signals and sensor data.

Inside nearly all modern electronics, tiny complex integrated circuits work by precision control of voltage. Signal voltages drive computations and also get interpreted as data.

Higher scale applications include electrical power distribution which steps high transmission voltages down for consumer device usage. Control systems also govern voltages in industrial processes.

Understanding voltage unlocks the ability to utilize electricity safely and effectively as a versatile utility across scales from microelectronics to large-scale power grids.