revision: Physics - Topic 2

QUESTIONS? Please ask me in comments :D
ELECTRICITY-
Voltage- The electrical push on electrons. Measured in volts (V) using a voltmeter (V).
Current - The rate of the flow of the electrons. Measure in amperes (A) using an ammeter (A).
An ammeter is always connected in a series circuit and a volt meter in parallel.
Remember-> Parallel = Voltmeter (PV - Phantom Virus ^^) Series = Ammeter (SA - Special A -the anime^^)

Conventional Current goes from positive to negative. [EXTRA: Actual current actually goes from negative to positive :)]

STATIC ELECTRICITY-
When you rub two insulators together you create friction and static electricity because the electrons on one of the insulators will be transferred to the other. One then becomes positively charged and the other negatively charged. Opposite charges attract and like charges repel.

CIRCUITS-
Before an electric current can flow, there must be a complete circuit, with no gaps. The current can flow through conductors but no insulators.
Parallel=
-More than one current path.
-Junctions.
-A1 = A2 + A3 = A4
-Vs = V1 = V2 <All the same, same voltage or push for the whole circuit.

Series=
-One current path.
-No junctions.
-A1 = A2 = A3 <The current is the same at all points
- Vs = V1 + V2

mA = milliamps ;) - Just incase.

[Electrons move, protons don't. Wires are full of electrons already, they're just waiting for that current - that little 'push' :)]


VOLTAGE IN...
SERIES = "the sum of the voltages across each of the component equals the voltage of the supply (the voltage is shared)" Vs = V1 + V2

PARALLEL = "the voltage across each component is the same as the supply" Vs = V1 = V2

CURRENT IN...
SERIES = "the current is the same all the way around the circuit."" A1 = A2 = A3

PARALLEL = "the sum of the currents in the branches equals the current entering the branches." A1 = A2 + A3 = A4 (Kirchoff's 1st law)

On battery cell diagrams, the longer lines represent the negative end and the smaller lines the positive :)

Parallel circuit bulbs are brighter!!

RESISTANCE-
Resistance is the ratio of voltage to the current, it is measure in Ohms (Ω)

Voltage = current x resistance
V=IR

Remember -> V=IR (VIRUS)
Current takes the path of least resistance.

FUSES-
Fuses are there for safety reasons and they work when the current increases and becomes higher than the fuses melting point. It will melt the fuse, breaking the circuit to prevents risks of electrocution and other hazards.
When the current increases, and the resistance decreases, the temperature raises too high and melts the fuses. It breaks the circuit, cutting the flow of electrons.

VARIABLE RESISTOR-
A variable resister is a component that allows you to increase or decrease the resistance in a circuit.

How it works-
It is made of many coils wrapped around again and again so that there is more space for the electrons to go through, slower if you wanted but you could also decrease the resistance as well as the surface area for these electrons.

When the slider moves, the electrons have to pass through more coils and this increased length means there is greater opportunity for collisions with the atoms.
The resistance, therefore, increase while the current decreases so there is less energy per second to the bulb making the bulb dimmer.