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BME 301: Biomedical Engineering

Introduction

• The prefix "bio" denotes something connected with life.

• Application of physics and chemistry on living systems leads to biophysics and biochemistry.

• The interconnection of medicine and engineering is termed biomedical engineering.

• Biomedical engineering involves applying knowledge from engineering and biological sciences for human benefit.

Major Aims of Biomedical Engineering

• Focus on utilizing methodologies and technology of physical sciences and engineering to address issues in living systems.

• Key areas include:

  • Diagnosis

  • Treatment

  • Disease Prevention

• Job titles in biomedical engineering include clinical engineers, hospital engineers, medical engineers, bioinstrumentation engineers, biomaterial engineers, and rehabilitation engineers.

Core Concepts in Electrical Engineering

Charge

• There are two types of charge:

  • Positive (carried by protons)

  • Negative (carried by electrons)

• Electron's charge (qe): 1.602 x 10^-19 C, the smallest charge measured in Coulombs (C).

• Time-dependent charge represented by q(t), and constant charge by Q.

Current

• Defined as the rate of change of charge through a point in time:

  • Measured in amperes (A); 1 A = 1 C/s.

• Formula:

  I = Q/t

• The direction of current is positive if a positive charge moves in the arrow's direction or if a negative charge moves opposite to the arrow.

Voltage

• Voltage (electric potential difference) is defined as the external work needed to transfer a charge in an electric field.

• Ohm's Law:

  • V = IRWhere V = voltage, I = current, R = resistance.

Power

• Power is the rate of energy transfer, measured in watts (W), where 1 W = 1 J/s.

• Formula:

  • P = W/t

• Different limits on energy conversion per unit time can apply.

Resistance

• A resistor limits current flow and is measured in ohms (Ω).

• Ohm's Law applies: V = IR.

• Series resistance calculation:

  • R_t = R_1 + R_2 + R_3 + ...

Circuit Types

Resistors in Series

• All resistors experience the same current; their total resistance equals the sum of their resistances.

Resistors in Parallel

• Resistors share the same voltage across them.

• The formula for total resistance is:

  • 1/R_t = 1/R_1 + 1/R_2 + 1/R_3 ...

Electric Circuits

• Electric circuits are pathways that allow for electron flow, typically powered by batteries.

• Key components include wires, switches, and resistive elements.

Example Analysis

Series Circuit Example

• Illustrated with four resistors (20Ω each and a 10Ω) connected to a 9V battery:

  • Total Resistance

    • R_eq = 20 + 20 + 20 + 20 + 10 = 90Ω.

  • Current through each: I = V/R_eq = 9V/90Ω = 0.1A.

  • Voltage drop across each:

    • V1 = V2 = V3 = (0.1A)(20Ω) = 2V;

    • Voltage divides and must sum to the total applied.

Parallel Circuit Example

• Analysis of a circuit with resistors of 1Ω, 2Ω, and 2Ω at 3V:

  • Total Resistance:

    • 1/R_eq = 1/1 + 1/2 + 1/2 = 0.50Ω

  • Total Current: I = 3V/0.50Ω = 6A.

  • Power dissipated across resistors calculated using P = VI.

Semiconductors

• Conductivity and resistivity lie between conductors and insulators.

• Key characteristics:

  • Governed by temperature and doping; N-type (extra electrons) and P-type (holes).

  • Common examples include silicon and germanium.

Potentiometers

• Used to measure EMF of cells or compare EMFs.

• Consists of a resistive wire where the voltage is proportional to the length of wire tapped.

• Applications in audio control, TVs, and transducers for displacement measurements.

Summary of BME 301: Biomedical Engineering

1. Introduction

   • Bio: Relates to life.

   • Biomedical Engineering: Merges medicine and engineering to benefit humans through techniques from biological sciences and engineering principles.

2. Major Aims

   • Use physical sciences and engineering methodologies to solve living system issues, focusing on diagnosis, treatment, and disease prevention.

   • Job Titles: Includes roles like clinical engineers, medical engineers, bioinstrumentation engineers, and rehabilitation engineers.

3. Core Concepts in Electrical Engineering

   • Charge: Positive (protons) and negative (electrons); smallest measurable charge is 1.602 x 10^-19 C.

   • Current (I): Rate of charge flow, measured in amperes (A); I = Q/t.

   • Voltage (V): Electric potential difference; V = IR (Ohm's Law).

   • Power (P): Rate of energy transfer (W); P = W/t.

   • Resistance (R): Limits current flow, measured in ohms (Ω); total resistance in series: R_t = R_1 + R_2 + ...

4. Circuit Types

   • Series Circuits: Same current, total resistance is the sum.

   • Parallel Circuits: Shared voltage, total resistance: 1/R_t = 1/R_1 + 1/R_2 + ...

5. Electric Circuits: Pathways for electron flow, powered by batteries, including wires and resistive components.

6. Examples

   • Series and parallel resistor analyses using total resistance, current, and voltage drops.

7. Semiconductors: Materials between conductors and insulators; conductivity influenced by temperature and doping (N-type and P-type).

8. Potentiometers: Measure EMF of cells, used in audio control, TVs, and transducers.