L3 U9 S04 Applied Ohm's Law
College Basics
College series of notes focusing on Ohm's Law and its applications.
Page 1: Key Concepts
Fundamental electrical terms: Watts (W), Amperes (A), Volts (V), Ohms (R).
Relationships: √P/R for Power, Voltage-Current relationships: V | I, P = IV, P = I²R, P = V²/R.
Page 2: Starter Activity
Task: Calculate the total resistance in a circuit with specified resistances.
Given: 12V supply, multiple resistances of 20.67 kΩ, 10 kΩ in series.
Page 3: Ready to Learn
Prepare for learning:
Wear ID badge.
Ensure bags are under the table.
Remove coats, hats, hoodies, and headphones.
Turn off mobile phones.
Have pen and paper ready.
Wait for instructions.
Engage actively in activities.
Page 4: Session Aims
Objective: Understand and apply Ohm's Law in various circuit configurations.
Calculate voltages in series and parallel circuits.
Determine currents in series and parallel circuits.
Page 5: Ohm’s Law - Recap
Ohm’s Law Formula: I = V/R.
Current is directly proportional to voltage across a circuit with respect to resistance.
Page 6: Find Voltage Example
Problem: Find V when I = 5A, R = 40Ω.
Calculation: V = I × R = 5A × 40Ω = 200V.
Page 7: Find Current Example
Work through finding current in a circuit with V = 100V and R = 2.2kΩ.
Calculation: I = V/R = 100V/2200Ω = 45.45mA.
Page 8: Find Resistance Example
Determine R when V = 24V, I = 2mA.
R = V/I = 24V/0.002A = 12000Ω (or 12kΩ).
Page 9: LED Application
LEDs require voltage and current constraints to prevent damage.
Typical values: 2V, 20mA.
Use a load resistor to manage the voltage from a 9V battery to protect LEDs.
Page 10: Calculate Resistor Value for LED
To find load resistor: R = V/I
V (drop) = 9V - 2V = 7V
I (required) = 20mA
R = 7V / 0.02A = 350Ω (use next standard value, 360Ω).
Page 11: Series & Parallel Key Points
In series: Current (I) is the same, different voltage drops across components.
In parallel: Voltage (V) is the same across components, different currents.
Page 12: Series Voltages
Example voltages for given resistors in a series circuit:
110V across series resistors 2kΩ, 1kΩ, 2.5kΩ.
Page 13: Series Currents
Note: In a series circuit all currents are equal irrespective of resistor values.
Current example: 20mA across multiple resistors.
Page 14: Example Calculations (Series Circuit)
Calculate voltage drops for resistors:
V1 = 50V across 1kΩ, V2 = 250V across 5kΩ, V3 = 150V across 3kΩ.
Page 15: Series Circuit Calculations
Determine total resistance and currents:
RT = R1 + R2, RT = 600Ω.
Use I = V/RT to find the current.
Page 16: Voltage Drops across Resistors
Multi-resistor drop calculation in series:
Total current = 52.38mA derived from RT = 1050Ω.
Voltage drops calculated for each resistor accordingly.
Page 17: Series Circuit Exercise
Practical exercise calculating voltage drops across given resistors with correct working shown.
Page 18: Recap on Series & Parallel Points
Important distinctions reiterated: series current vs. parallel voltage behavior.
Page 19: Parallel Voltages
Note: In parallel, voltage remains constant across all components.
110V across all resistors connected in parallel.
Page 20: Parallel Currents
Analyze currents in a parallel setup demonstrating Ohm's Law.
Page 21: Parallel Circuit Example 1
Use Ohm's law to find currents in a parallel circuit.
R1, R2, R3 = 5kΩ, 3kΩ, 1kΩ, with supply 230V.
Total current IT = 352mA calculated from individual currents I1, I2, I3.
Page 22: Parallel Circuit Example 2
Calculate currents with different resistor values (e.g., 470W, 220W, 560W); similarly derive IT.
Page 23: Parallel Circuit Exercise
Follow through theoretical problem solving for various parallel circuits with detailed working.
Page 24: Combinational Circuits Overview
Combination of series and parallel components requires careful application of Ohm's Law.
Page 25: Combinational Example 1
Begin with finding equivalent resistances in mixed circuits.
Page 26: Combinational Circuit Continued
Calculate total resistance and derive supply current, then voltage drops across components.
Page 27: Completing the Circuit Calculations
Return to calculate missing current variables across the circuit based on derived voltage drops.
Page 28: Important Note on Voltage
Emphasize selecting the correct voltage across individual components for current analysis, not just supply voltage.
Page 29: Combinational Exercise 3
Practice determining all currents and voltage drops within given circuit setup, ensuring clarity in working.
Page 30: Session Aims Recap
Comprehensive session aim: recall, demonstrate understanding, apply Ohm’s Law across series and parallel circuits.
Page 31: References
Attributed resources under Creative Commons related to LED image.