Basic Electricity - Senior Secondary 1 - Chemical sources of electromotive force

Chemical sources of electromotive force

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TERM: 3RD TERM

WEEK EIGHT

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: BASIC ELECTRICITY

Topic: CHEMICAL SOURCES OF ELECTROMOTIVE FORCE

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Define energy

II.) Define electrical power

III.) Test the conditions of the cell

IV.) Connect cells in series and parallel

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher explains the meaning of energy and electrical power to the students

Students listens attentively to the teacher                                                                          

STEP 2

EXPLANATION

Teacher guide students to test the conditions of a cell and also connect cells on series and in parallel.

Students exhibit attentiveness and active engagement

STEP 3

NOTE TAKING

The teacher writes a summarized

note on the board

The students

copy the note in

their books

 

NOTE

CHEMICAL SOURCES OF ELECTROMOTIVE FORCE

Energy

Energy is the capacity to do work or produce heat. It exists in various forms such as kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat), chemical energy (energy stored in chemical bonds), and electrical energy (energy associated with the movement of electrons).

Electric Power

Electric power is the rate at which electrical energy is transferred by an electric circuit. It is measured in watts (W) and is calculated using the formula:

      P = IV

     Where:

     - P  = electric power in watts (W).

     - I = electric current in amperes (A).

     - V is the electric potential difference (voltage) in volts (V).

Testing the Condition of a Cell

The common method to test the condition of a cell, especially in household batteries like AA or AAA batteries, is to use a multimeter set to measure voltage (volts).

  1. Ensure the multimeter is set to the appropriate voltage range, usually DC volts.
  2. Connect the multimeter's probes to the positive (+) and negative (-) terminals of the cell.
  3. The multimeter will display the voltage of the cell. Compare this voltage to the nominal voltage rating of the cell. If the measured voltage is significantly lower than the nominal voltage, it indicates that the cell may be depleted or nearing the end of its usable life.
  4. It's important to note that this test provides an indication of the cell's condition but may not provide a comprehensive assessment of its overall health or capacity to deliver current under load. For more detailed testing, specialized equipment may be required.

Connecting cells in series and parallel

Connecting cells in series and parallel allows you to achieve different voltage and current configurations, respectively.

  1. Connecting Cells in Series:

When cells are connected in series, their voltages add up while the current remains the same. This increases the total voltage of the circuit.

I.) Arrange the Cells: Place the cells side by side so that the positive terminal of one cell is connected to the negative terminal of the next cell.

II.) Connect the Terminals:  Use conducting wires to connect the positive terminal of the first cell to the negative terminal of the second cell. Continue this pattern until all cells are connected.

The unconnected terminals at both ends of the series arrangement will be the positive and negative terminals of the entire battery pack.

III.) Result: The total voltage of the battery pack is the sum of the voltages of all the individual cells connected in series.

  1. Connecting Cells in Parallel

When cells are connected in parallel, their voltages remain the same while the total current increases. This increases the capacity or current capability of the circuit.

I.) Arrange the Cells: Place the cells side by side so that all positive terminals are connected together and all negative terminals are connected together.

II.) Connect the Terminals: Use conducting wires to connect all the positive terminals of the cells together and all the negative terminals together. Each cell is connected directly across the common positive and negative terminals.

III.) Result: The total voltage of the battery pack remains the same as that of a single cell, but the capacity or current capability increases as the total current is the sum of the currents of all the individual cells connected in parallel.

EVALUATION: 1. Define energy

  1. What do you understand by electrical power
  2. How do you test the condition of a cell?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively