Chapter 6 - Measuring Electricity Flashcards
Current
- The rate at which electrons are flowing in a circuit. (Amps)
- Can be direct (DC), electrons flow the same direction
or - alternating (AC), electron shuffle back and forth (power points)
Voltage
The difference in charge between two points
- measured by how much energy is supplied by the battery being used by components (volts)
Australian power points and transformers
- Australian power points supply 240V
- A transformer may be used to reduce the voltage, like an appliance for example using 6v (phone).
Adding batteries
Adding batteries leads to all their voltage added up.
Resistance
- Force that opposes the current (ohms)
- Electrons moving through the circuit are blocked by atoms of circuit components.
Photovoltaic Cells
convert solar energy into electrical energy, sunlight knocks electrons off silicon crystals into a circuit which generates a current.
Wet and Dry Cells
Wet Cells - conducting electrodes (metal) submerged in liquid electrolyte.
Dry Cells - One electrode wrapped in another, these are small and dont leak.
Resistance in Wires
- Connecting wires also have resistance
- Material, metals have low resistance
- Length, the longer, the more resistance
- Thickness, the thicker, the less resistance
Resistors
Used to reduce the current, as too high of a current could damage appliances.
Variable resistors allow you to control the current, making one control the speed of a motor or brightness of light bulbs.
Conductors
Metals are conductors (low resistance)
- Copper is good as it is cheap and used in circuits
- Aluminum is excellent, but expensive, used for transmission towers
- Tungsten and nichrome are poor, they give off thermal and light, used for light bulbs
Insulators
- Materials with high resistance
- Wood to hold up power lines
- Rubber and plastics to coat wires preventing leakage of electricity
