Unit 8 Making Use of Electricity

Topic

Understanding voltage

Curriculum Link

8.4 Voltage

Estimated Lesson Time

80 minutes

Introduction

Voltage is a difficult concept for junior secondary students. Starting with 'Task 1: matching the voltage of bulbs to the batteries', students could find that a bulb is designed with specific voltage to glow satisfactory. In Task 2, students are required to connect the concepts 'voltage', 'current' and 'energy' together. Then, they will explore the importance of using proper voltage in electric appliances. Finally, students are asked to examine the 'power ratings' label of electric appliances. Thus, they will be aware that electrical energy supplied in different countries using different voltage.

Key Question

Why light bulbs are labelled with different voltages?

Learning Objectives

In this activity, the students should be able to

  1. understand battery is an energy source;
  2. explain why light bulbs are labelled with different voltages (SP 5);
  3. use analogue to explain the relation amongst energy, voltage and ampere (SP 6);
  4. aware of the proper use of voltage in electrical appliances;
  5. know that electrical energy supplied in different countries use different voltage.

Teaching Plan

Task (Time) Brief Description Materials Objectives

Engagement & Explanation
(25 min)

Students are engaged to attend to the concept 'voltage' by matching bulbs and batteries in Task 1:Lighting up an electric torch. In this task, battery will be introduced as the source of energy. In addition, the concept 'voltage' becomes the key to match bulbs and batteries.

 (1) & (2)

Elaboration & Explanation
(20 min)

In Task 2, ask students to explore the brightness of bulb with the use of different number of batteries. Based on this exploration, teacher explains the relation amongst the concepts 'energy', 'voltage' and 'current'.  Students are asked to think an analogy to relation 'voltage' to both 'energy' and 'current'.

(2) & (3)

Explanation & Exploration
(20 min)
  • In 'Task 3: Using proper voltage', students explore and explain the brightness of light bulb using different batteries.
  • (Optional): Students could be asked to explain the effect of Extra-high voltage. This is an interesting but dangerous experiment. This effect is related to our daily experiences 'Lightning'

    Ref(video): High voltage experiment:
    https://www.youtube.com/watch?v=c9rsQvb8SZE
 (2) & (4)

Exploration & Elaboration
(15 min)

In Task 4, teacher could show students some electric appliances, such as electric fan, dryer, electric boiler. Then, ask students to examine the 'power ratings' labels. In addition, ask students to distinguish the appliances used in Hong Kong and USA/Japan.

 (4) & (5)

*Apparatus and materials required: