Lesson Notes By Weeks and Term v3 - Senior Secondary 1

Lesson Video

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Performance objectives

• Draw electric field lines for different charge arrangements.
• Explain and calculate electric current.
• Assemble a simple electric circuit.
• Distinguish between conductors and insulators.
• Define electrical resistance and calculate electrical work.

Lesson summary

Students should be Able to: Draw electric linesof for ce around:is olate positivecharge;is olate negativechargetwo like chargesplaced near eachothertwo unlikecharges placednear each other. generate acontinuous flowof charges explain electriccurrent. set up a simpleelectric circuit. Distinguishbetweenconductors and insulators. Define resistanceas opposition to flow of charges(electrons). Calculate the electrical workdone in a givencircuit.

Lesson notes

An electric field is a region of space around an electrically charged particle or object within which a charged object would experience an electrostatic force. It is a vector quantity, meaning it has both magnitude (strength) and direction. The direction of the electric field at any point is defined as the direction of the force that a small positive test charge would experience if placed at that point. Electric field lines are imaginary lines used to visualize electric fields. They represent the path a small positive test charge would follow if placed in the field.

Properties of Electric Field Lines: They originate from positive charges and terminate on negative charges. If only one type of charge is present, they extend to or from infinity. They never intersect each other. If they did, it would mean the electric field has two directions at that point, which is impossible. They are closer together where the electric field is stronger and farther apart where it is weaker. They are always perpendicular to the surface of a conductor. They never form closed loops (unlike magnetic field lines).

Drawing Electric Field Patterns: a)

Isolated Positive Charge: Lines radiate outwards from the positive charge. Arrows point away from the charge. Symmetry is maintained. ``` + /|\ / | \ / | \ \ | / \ | / \|/ ``` b)

Isolated Negative Charge: Lines radiate inwards towards the negative charge. Arrows point towards the charge. Symmetry is maintained. ``` ^ /|\ / | \ / | \ --->o - |\ /| | \ / | | \ / | | \ / | | \ / | | O | (Lines connect from + to -) | / \ | | / \ | | / \ | | / \ | |/ \| ``` Electric current is defined as the rate of flow of electric charge. It is the movement of charge carriers (e.g., electrons in metals, ions in electrolytes) from one point to another. The SI unit for current is the Ampere (A).

Formula: Current (I) = Charge (Q) / Time (t) `I = Q / t` Where: I is current in Amperes (A) Q is charge in Coulombs (C) t is time in seconds (s)

Generating a Continuous Flow of Charges: For a continuous flow of charge (i.e., a continuous current), a closed circuit and a source of electromotive force (e.m.f.) are required. A battery or a generator provides the e.m.f., which is the energy supplied per unit charge, effectively "pushing" the charges around the circuit. This continuous push maintains the potential difference required for charges to flow continuously.

Example 1 (Current Calculation): If 300 Coulombs of charge pass through a point in a conductor in 2 minutes, calculate the current flowing.

Solution: Given: Charge (Q) = 300 C Time (t) = 2 minutes = 2 * 60 seconds = 120 s Formula: `I = Q / t` `I = 300 C / 120 s` `I = 2.5 A` Therefore, the current flowing is 2.5 Amperes. A simple electric circuit is a closed loop through which electric current can flow.

It typically consists of: Power Source: (e.g., battery, cell) provides the e.m.f.

Conductor: (e.g., copper wires) provides a path for current flow.

Load: (e.g., bulb, resistor) converts electrical energy into other forms (light, heat).

Switch: (optional but useful) to open or close the circuit, controlling current flow.

Circuit Diagram Symbols: Battery: `---| |---` (long line for positive, short for negative)

Wire: `-----` Bulb: `---(O)---` or `---(x)---` Switch (open): `---/ ---` Switch (closed): `-----` (like a continuous wire)

Resistor: `---/\/\/\---`

Real-life applications

Safety in Electrical Installations and Appliance Usage: The distinction between conductors and insulators is paramount for electrical safety in Nigerian homes and industries. Knowledge that copper is a good conductor explains why wires are made of it, while rubber/plastic are insulators and used as wire coatings to prevent shocks and short-circuits. Earthing systems in buildings, mandated by electrical safety standards, rely on good conductors to safely channel fault currents to the ground, protecting lives and properties from electrocution or fire. This is particularly relevant in areas with fluctuating power supply.

Power Transmission and Energy Efficiency: Understanding resistance, current, and power is crucial for the efficient transmission of electricity from power generating stations (e.g., Kainji Dam, Egbin Thermal Plant) to end-users across Nigeria. High resistance in transmission lines leads to significant energy loss (power dissipated as heat, `P = I2R`). This is why power is transmitted at very high voltages and low currents (to reduce `I2R` losses) over long distances, then stepped down for domestic use. This knowledge helps in appreciating the challenges and engineering solutions in Nigeria's power sector.

Operation of Common Household Appliances: Every electrical appliance in a Nigerian home – from the electric fan and refrigerator to the pressing iron and kettle – operates on the principles of electric current, resistance, and power. Students can relate the wattage rating on appliances (e.g., "1500 W" on a pressing iron) to the amount of power it consumes and the work it does, and how this translates to electricity bills. Understanding these concepts helps in making informed decisions about energy conservation and appliance selection. ---

Teacher activity

• Show lines of for ce using at est positivecharge
• Demonstratethe productionof acontinuousflow of charge:Chemicalenergy Heat energy Mechanicalenergy Solar energy
• Illustrate the importance of fuses in electric circuitsby setting upa short-circuit

Evaluation guide

• Formative Assessment Strategies:
• Observation: Observe students during practical activities (e.g., setting up circuits, testing conductivity) for their understanding and practical skills.
• Questioning: Ask probing questions throughout the lesson to check for comprehension of concepts and definitions.
• Mini-Whiteboards/Think-Pair-Share: Have students sketch field patterns or solve quick problems on mini-whiteboards, or discuss answers in pairs before sharing with the class.
• Check for Understanding: After each key concept, ask students to explain it in their own words.

Reference guide

• Chartsshowing the lines of for ce
• Two differentmetals. A cell,the rmocoupl,a coil and amagnet, solarcells, cells,key,ammeters,voltmeters,resistors.
• Cells, resistors,ammeters,voltmeters,cell, bulb,differentmetals,plastics, wood,ceramics, etc
• Different typesof wire.
• Electric motor,pulley set of weight, stopclock.
• Fuse wire,bulbs