Notes (textbook ch1)

Physical computing Introduction/Chapter 1

• Transduction: conversion of one form of energy into another
• All electrical and electronic devices exploit the fact that electrons have the tendency to go from a point of greater electrical energy to a point of lesser electrical energy
• provide a positive connection (greater energy, or power), a negative connection (lower energy, or ground), and a conductor through which the electrons flow. [then] the electrons will travel from power to ground
• A circuit - closed loop containing a source of electrical energy (a battery) and a load (a light bulb)
• A switch - a break in the circuit that stops the electrons from flowing. By closing the switch, you close the break in the circuit and allow the electrons to flow again 
• Every component you put into your circuit has certain electrical characteristics 
• battery can provide a certain amount of electrical energy, and the light bulb can resist a certain amount of electrical energy
• If you provide too much electrical energy, the wire inside the light bulb will melt, breaking the circuit

The 3 basic electrical characteristics that come into play in every circuit:

• Voltage: relative level of electrical energy between any two points in the circuit
• measured in volts; V
• Current: amount of electrical energy passing through any point in the circuit. 
• measured in amperes/amps; 
• Resistance: amount any component in the circuit resists the flow of current 
• measured in ohms; Ω
• Ohm’s Law: Voltage = Current × Resistance (likewise, Current = Voltage/Resistance and Resistance = Voltage/ Current

-

• Short circuit:  circuit without enough resistance in its load.  If circuit does’t use enough energy, it will just go right back into the battery, heating it up, and eventually blowing it up
• open circuit: etc a switch (off)
• closed circuit: switched (on)
• electrical power/wattage: combination of current and voltage
• watts = volts × amps
• amps = watts/volts or volts = watts/amps

Electricity always favors the path of least resistance to ground.

All the electrical energy in a circuit must be used.