## Fields (10 minutes)

• Scalar fields are a number at every point in space
1. SWBQ: write down an example of a scalar field.
2. Temperature as an example
• Get students to stand up and distribute throughout the room, with their small whiteboard, and write a number between 0 and 10 on it
• Now have students represent the field $20 x \cos(\pi y/L)$ C/m, where $L$ is the length of the room
• We might be really interested in finding where the field is constant
3. Electrostatic and gravitational potential are other examples
• GEM § 2.3.2
4. Bring in a voltmeter with attached wires and actually point to various points in space stating that it would measure a value at every point in space. We return to this visual aid often, but at some stage (perhaps this first day) it is important to point out two things:
• How a voltmeter actually works and that you have to set the zero of potential somewhere.
• The fact that voltmeters do NOT work the way you theoretically want them to may be an issue, especially for experimentalists. Nevertheless, we have found that STUDENTS often miss the fact that what a voltmeter measures and what you mean by electrostatic potential have anything to do with each other, even in principle.
• GVC § Voltmeters

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