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• Static electricity is all about electrons being transferred from one place to another.
• Rubbing polythene cloth on rods transfers electrons, causing them to become negatively charged and attract positively charged items.
• Balloons stick to walls because they become negatively charged due to the transfer of electrons and then stick to the positive charges on the wall.
• Hair stands on end when touching a Van de Graaff generator because it becomes negatively charged and the electrons repel each other, causing the hair to stand up.
• Metal slides do not cause a charge because metals are good conductors, allowing electrons to freely flow.
• Static electricity can be used for spraying bike frames and electrostatic precipitators to get an even finish and remove pollutants, respectively.
• Dangers of static electricity include explosions from sparks between charged planes and fuel tankers, which can be prevented by using an earthing strip made of metal.
• Symbols used in electrical circuits include cells (a push to drive electrons), batteries (two or more cells), bulbs (a circle with a cross), resistors (a rectangle with two lines), fuses (a safety device to stop fires caused by high currents), and variable resistors (resistors that can alter resistance).
• Increasing the temperature of a regular resistor increases resistance because the positive metal ions vibrate more, impeding the flow of electrons.
• Thermistor: A special kind of resistor made of silicon, where increasing temperature decreases resistance and decreasing temperature increases resistance.
• LDR (Light Dependent Resistor): A resistor whose resistance decreases with increasing light levels and increases with decreasing light levels.
• Diode: A component that only allows current to flow in one direction, shown by the direction of the arrow. A light emitting diode emits light at the same time.
• Wire: Represented as a straight line.
• Switch: An open switch breaks the circuit, while a closed switch completes the circuit.
• Voltmeter: Measures the potential difference (voltage) of a circuit and is connected in parallel to the component being measured.
• Ammeter: Measures the current of a circuit and is connected in series to the main part of the circuit.
• Circuit Rules: In a series circuit, the brightness of bulbs decreases with each bulb added, and the cell runs out of charge quickly. In a parallel circuit, the brightness of bulbs remains the same, but the cell runs out of charge twice as quickly as with a single bulb.
• In a series circuit, the current is the same everywhere and the voltage of the individual components adds up to what is coming out of the cell. In a parallel circuit, the voltage is the same everywhere and the current adds up.
• Ohm's law states that the current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor. The resistance of some components, such as the filament bulb and the diode, do not obey Ohm's law.
• Resistance has the unit of ohms and in a series circuit, the resistance of the individual components adds up to the total resistance of the circuit.
• To calculate potential difference, the formula V = IR is used, where V is voltage, I is current, and R is resistance.
• When a switch in a circuit is closed, the total resistance of the circuit decreases, and the current increases.
• In order to obtain results for how current varies with potential difference, a circuit diagram must include lamps, an ammeter connected in series, a voltmeter added in parallel, and a variable resistor.
• Ohm's law: The current through a conductor between two points is directly proportional to the voltage against two points.