Electric Current

Grade 9 · General Science

Semester 2 | Period 5 | Week 27

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Subject: General Science

Semester: 2

Period: 5

Week: 27

School Name:
Teacher’s Name:
Subject: General Science
Grade Level: Grade 9
Date:
Lesson Duration: 45 minutes
Week & Period: Week 27, Period 5
Topic: Electric Current
Sub-topic: Types, Effects, Measurement, and Ohm’s Law

Learning Objectives
By the end of the lesson, students should be able to:

  1. Differentiate between direct current (DC) and alternating current (AC).
  2. Explain the effects of electric current on metals, non-metals, and aqueous solutions.
  3. Measure electric current using an ammeter and apply Ohm’s Law.

Previous Knowledge
Students already know:
• Basic concepts of electricity and magnetism.
• Safety precautions when handling electrical devices.

Instructional Materials
• Textbook: General Science textbooks for Grade 9
• Teaching aids: DC and AC source setups, ammeter, wires, resistors, metals, non-metals, aqueous solutions, chart of S.I. units
• Students' notebooks and writing materials

Lesson Development – ABC Model

A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Activity: The teacher will ask the class:
• Can you name some devices that use batteries and others that use household electricity?
• What do you think happens when electric current passes through a metal or water?
The teacher will record their responses on the board.
Teacher’s Role: Guide discussion, correct misconceptions, and link to prior knowledge of electricity.
Learner’s Role:
• Share prior experiences with DC and AC devices.
• Participate actively in discussion.

B – Building Knowledge (Main Lesson Body)

Time: 25–30 minutes

Teacher’s Role:

  • Explain direct current (DC):
    • Electric current flows in one direction.
    • Examples: batteries, torch cells, calculators, small electronic devices.
  • Explain alternating current (AC):
    • Electric current changes direction periodically.
    • Examples: household electricity, power from generators.
  • Demonstrate the effects of electric current:
    • Metals: conduction of electricity, heating (e.g., filament bulb)
    • Non-metals: generally do not conduct, can be affected in special cases
    • Aqueous solutions: conduct electricity if ions are present; demonstrate with electrolysis of salt solution.
  • Show how to measure current using an ammeter:
    • Proper connection in series with the circuit
    • Safety precautions: avoid exceeding current rating, ensure correct polarity.
  • Introduce Ohm’s Law: V = I × R
    • Explain variables: V = voltage (volts), I = current (amperes), R = resistance (ohms)
    • Solve simple numerical problems using Ohm’s Law.
  • Discuss S.I. units for current (ampere), voltage (volt), and resistance (ohm).

Learners’ Activities:

  • Observe DC and AC circuit demonstrations.
  • Conduct experiments to test current effects:
    • Pass current through a metal wire, non-metal, and salt solution.
    • Observe heating, conduction, or electrolysis effects.
  • Measure electric current in simple circuits using an ammeter; record readings.
  • Solve Ohm’s Law problems individually or in groups:
    • Example: Find current if V = 12 V and R = 4 Ω → I = V/R = 12/4 = 3 A
    • Example: Find resistance if V = 9 V and I = 3 A → R = V/I = 9/3 = 3 Ω

Assessment Checks:

  • Ask learners to explain the difference between DC and AC.
  • Observe correct usage of the ammeter in circuits.
  • Quick oral questions:
    • “State Ohm’s Law.”
    • “What is the S.I. unit of resistance?”
    • “Give one example of DC and AC.”

Notes (Expanded & Detailed):

  • DC electricity is common in batteries and small electronics.
  • AC electricity is used in household appliances and grid power.
  • Safety precautions:
    • Avoid touching live wires.
    • Do not exceed recommended voltage/current.
    • Ensure proper insulation.
  • Real-life applications of electric current effects:
    • Electroplating: depositing metal layers
    • Heating: electric irons, kettles
    • Electrolysis: producing gases, chemical reactions

Practical Activities / Experiments:

  1. DC vs AC Demonstration: Use battery (DC) and mains simulator (AC) to show current direction with an ammeter.
  2. Current Effects Experiment: Pass current through metal wire (heating), non-metal (no conduction), and salt solution (electrolysis).
  3. Measuring Current: Connect an ammeter in series and record current in different simple circuits.
  4. Ohm’s Law Problems: Solve numerical examples in groups using real circuit measurements.

Assignments / Homework:

  1. Identify three DC devices and three AC devices at home and explain how they use current.
  2. Solve five Ohm’s Law problems: given V and R, calculate I; given I and V, calculate R.
  3. Observe a salt solution electrolysis experiment at home (or school) and record effects.

Extra Questions / Quick Assessment:

  • What is the main difference between DC and AC?
  • How do metals, non-metals, and solutions respond to electric current?
  • State Ohm’s Law and give the S.I. units of V, I, and R.
  • Explain one practical application of electric current in everyday life.

 

C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary:
• Recall types of electric current and their sources.
• Review the effects of current on different materials.
• Summarize how to measure current and apply Ohm’s Law.

Evaluation Method (Expanded):
• Exit slip/quiz: Students will write short answers to:
– Give one example each of DC and AC devices.
– Explain what happens when current passes through a metal.
– Calculate the current if V = 12 V and R = 4 Ω.
• Teacher will collect and quickly review for understanding.
• Provide oral feedback before class ends.

Assignment (Expanded):
Follow-up Activity:
• Students identify DC and AC devices at home, measure current in simple circuits (under supervision), and solve one numerical problem using Ohm’s Law.

Differentiation / Inclusive Strategies
• Struggling Learners: Provide guided examples and step-by-step demonstrations for Ohm’s Law and measurements.
• Advanced Learners: Challenge them to analyze mixed circuits or derive Ohm’s Law from first principles.
• Students with Disabilities: Use tactile circuit models, assistive devices, and peer support for hands-on activities.

Teacher’s Reflection (After Class)
• What worked well? ______________________________________________________
• What needs improvement? _________________________________________________
• Students’ engagement level: □ High □ Medium □ Low