UNIT OVERVIEW

Have you ever wondered why your hair stands up when you pull off a woollen jersey? Or why you sometimes get a small shock when touching a metal door handle? These everyday experiences are caused by static electricity — electric charges that have built up on objects.

In this unit, you will learn about the electrostatic force — an invisible force between charged objects. This force is much stronger than gravity at small scales. It holds atoms together, causes lightning, and even makes your smartphone's touchscreen work.

By the end of this unit, you will be able to:

• Identify the two types of electric charge and explain how objects become charged
• Describe and predict the forces between charges (attraction and repulsion)
• Explain how charged objects can attract neutral objects through polarisation
• Apply the principle of conservation of charge to solve problems
• Understand that charge comes in discrete packets (charge quantisation)
• Calculate the total charge on an object using the elementary charge formula

Real-life applications of electrostatics:

• Photocopiers and laser printers use electrostatic attraction to transfer toner onto paper
• Lightning rods on buildings safely conduct electric charge to the ground
• Electrostatic spray painting uses charged paint droplets to coat cars evenly, reducing waste
• Air purifiers charge dust particles so they stick to collection plates

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