Physics: Static Electricity and Circuits

Static Electricity

• Static electricity is a build-up of charge in an object that remains at rest.
• Protons are positively charged subatomic particles that cannot easily move.
• Electrons are negatively charged subatomic particles that can move from one substance to another.
• A neutral atom has equal numbers of protons and electrons.
• A substance is positively charged if it has fewer electrons than protons.
• A substance is negatively charged if it has more electrons than protons.
• Rubbing materials together does not create electric charges, it transfers electrons from one material to the other.

Electrical Energy: Circuits

• Electrical circuits consist of a power supply, a load, and conductors to allow electricity to flow.
• Loads are components which convert electrical energy into other forms of energy, such as light globes.
• Conductors allow electrons to flow easily, such as metals like gold and iron.
• Insulators do not allow electrons to flow easily, such as rubber, wood, plastic, and glass.

Electric Circuit Basics: Series Circuits

• In a series circuit, components are connected one after another.
• The current is the same throughout the circuit.
• The sum of the voltage drops across each load equals the voltage of the power supply.
• When a load in a series circuit is removed or breaks, the circuit is broken and all components stop working.
• As more loads are added to a series circuit, the brightness of the globes decreases.

Electric Circuit Basics: Parallel Circuits

• In a parallel circuit, components are connected on different branches.
• The sum of the current flowing through each branch equals the overall current of the circuit.
• Voltage is consistent across each load.
• If one load in a parallel circuit is removed or breaks, the other loads will continue to work.

Electrical Energy: Voltage, Current, and Resistance

• Voltage is a measure of the potential difference between two points in a circuit, which represents the amount of energy that charges (electrons) have.
• Current is the rate of flow of charges (electrons) through a circuit.
• Resistance opposes the flow of current and the higher the resistance, the lower the current flow.
• An ammeter is used to measure current in amps or milliamps.
• A voltmeter is used to measure the voltage (potential difference) in volts.

Ohm’s Law

• Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage across its ends.
• An Ohmic conductor is a conductor that obeys Ohm’s Law.
• The relationship between current, voltage, and resistance is given by: Voltage = Current x Resistance
• The current through an Ohmic conductor is constant regardless of voltage.

Series and Parallel Circuits

• In a series circuit, components are connected one after another.
• In a parallel circuit, components are connected on different branches.
• The current is the same through all components in a series circuit.
• The voltage is the same across all components in a parallel circuit.

Ammeters and Voltmeters

• An ammeter is used to measure current. It must be connected in series with the circuit.
• A voltmeter is used to measure voltage. It must be connected in parallel with the circuit.

Errors in Measurement

• Random errors occur when estimations are made in reading measurement scales.
• Systematic errors occur due to incorrect use of equipment or limitations of the equipment.
• Random errors can be reduced by repeating measurements and averaging the results.
• Systematic errors can be reduced by using the equipment correctly and calibrating it.