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This video explains the angles of elevation and depression.

Video 1: How to calculate the area and circumference of circles and semi-circles
Video 2: Examples pertaining to calculating the area and circumference of circles and semi-circles
Video 3: Common mistakes made when calculating the area and circumference of circles and semi-circles

Note: After watching each video, click on the 'back button' to return to the VLE

• Determine the variables that affect how charged bodies interact.
• Predict how charged bodies will interact.
• Describe the strength and direction of the electric field around a charged body.
• Use free-body diagrams and vector addition to help explain the interactions.

Electric charge comes in two varieties, which we call positive and negative. Like charges repel each other, and unlike charges attract each other. Thus, two positive charges repel each other, as do two negative charges. A positive charge and a negative charge attract each other.

How do we know there are two types of electric charge? When various materials are rubbed together in controlled ways, certain combinations of materials always result in a net charge of one type on one material and a net charge of the opposite type on the other material. By convention, we call one type of charge positive and the other type negative.