This post was supposed to be entirely on electricity, but I missed out a bit on car safety last time, so here it is -
Stopping distance = thinking distance + braking distance
Internal factors that effect thinking -
- pets
- kids
- phones
- smoking
- eating
- drinking
- radio
- beautifying
- reading
External factors that effect thinking -
- idiots in other cars
- hot models
- illness
- drugs
- alcohol
- caffine
- physical inabilities
- animals
Other factors - AGE
Factors that effect breaking distance -
- quality of brakes
- tires (width and grip)
- road surface (stoney/smooth)
- grass / mud / sand
- ice / snow / surface water / wind / other weather factors)
Okay, and now on to electricity -
Current - is the flow of electrons around a circuit
Voltage - is the push driving the electrons
Resistance - is something slowing down the current
Ammeter - is something that measures the current (Amps/A, resistance = voltage/current)
Electrons flow the opposite way to a conventional current because they're negatively charged and flow from negative to positive.
The current in a series circuit is the same at every point, whilst the current in a parallel circuit is divided up.
If a bulb is added to a circuit, both bulbs will get dimmer (providing they're the same watt).
Ammeters are always connected to a circuit in series, whilst a voltmeter is connected in parallel.
Resistance can be calculated using Ohm's law -
Resistance (Ohms) = Voltage (V) / Current (I)
Resistance is also shown using current-voltage graphs
Think wires have more resistance than think ones. If you halve the cross section of a wire, the resistance doubles because there's half as much space for the electrons to move.
Different materials also have different resistance, for example, a nichrome wire has more resistance than a copper one of the same size because the atoms in nichrome hold the electrons tighter then copper.
LDR - is a light dependant resistor. The more light that falls on it, the less resistance there is.
Thermistor - is temperature sensitive. As the temperature increases, the resistance decreases.
PLUGS!
There's my plug diagram ^
When wiring a plug, you must -
- not have extra wire poking out of the pin block
- screw it down fully
- make sure no excess wire will be pinched when the lid is put down
- make sure the cable grip has a tight grip on the cable
Earth wires - are always used in appliances with a metal case. If a fault develops and the live wire touches the metal case, a surge in the current does down the earth wire, causing the fuse to blow. This makes the appliance insulated.
Live wires - alternate between high positive and high negative voltage and an average of about 250V.
Neutral wires - are always at 0V.
Fuses - are designed for safety. If a fault develops, a large current flows through the the fuse and causes it to melt. This breaks the circuit and protects the appliance and user.
Power = Voltage x Current
(W = V x I)
MCB - is a a miniature circuit breaker, aka a resettable fuse that you can turn back on after a power surge.
RCD - is a radical current device, which looks at what goes in and out of an appliance and can detect when an appliance is using too much current.
WHOOOOP.
That's all the work I've done on Physics, which is lucky because I have my exam tomorrow.
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