Electrical Circuits

• Current electricity involves examining electric current at junctions in circuits and understanding potential difference measurements.
• The study of current electricity covers common symbols for components, the effects of changing circuit components on current, current and voltage behavior in series and parallel circuits, and the relationship between watts and joules per second.

Key Terms

• Attraction involves forces bringing objects together, often due to opposite charges or poles.
• An atom is the basic building block of matter.
• Repel is to push away, often used in the context of like charges or poles.
• Electron is a subatomic particle with a negative charge and negligible mass.
• Static electricity refers to the accumulation of electric charge on an object.

Introduction to Electrical Circuits

• Light bulbs give out light.
• A cell pushes charges around a circuit.
• A battery comprises two or more cells.
• Wires connect circuit parts.
• A switch turns the current on and off.
• A voltmeter measures potential difference (voltage).
• An ammeter measures electric current.

Circuit Components & Symbols

• Circuit components include lamps, batteries, cells, switches, voltmeters, ammeters, resistors, and motors.
• Electric charge flows around a circuit are called electrons.
• Electrons are negatively charged and flow away from the negative side of a cell or battery towards the positive side.
• In circuits, copper wires are usually used.

Electric Current

• Electric current is the flow of electrons, which are negatively charged particles.
• Electric current flows only when there is a complete circuit.
• Series circuits have only one route for the current to take.
• Parallel circuits have junctions that allow the current to take different routes.

Current Measurement

• An ammeter, connected in series, measures the current in a circuit.
• The units for current are amperes (A).

What is Current?

• Current denotes the rate of flow of charge.
• Millions of electrons flow through a bulb each second when a switch is closed.
• A higher electron flow equates to a higher current; a lower electron flow means a lower current.

Series Circuits

• Series circuits: all components are connected one after another in a single loop.
• If one part of a series circuit stops working, the entire circuit ceases to function.
• Only one pathway exists for electrons to flow through.
• Series circuits are cheaper and use less power.

Parallel Circuits

• Parallel circuits: components are connected in separate branches.
• If one branch in a parallel circuit stops working, the other branches continue to work.
• Two or more pathways exist for electrons to flow through.
• Parallel circuits are generally more expensive as they use more power.
• If one bulb breaks in a parallel circuit, the other bulbs remain lit.

Current Behavior in Circuits

• In a series circuit, the current is the same everywhere.
• In a parallel circuit, the current splits at junctions.
• Series circuit experimental data: using a two-bulb circuit, if the ammeter reading at position A1 is 0.45A, the same reading will be observed at positions A2 and A3.
• This demonstrates that the current remains constant throughout a series circuit.
• Parallel circuit experimental data: using a two-bulb circuit, if the ammeter reading at position A1 is 1.80 A, the ammeter might read 0.9 A at A2 and A3, and 1.80 A at A4.
• This demonstrates that the current in a parallel circuit is shared between the pathways, with the total current being higher than in a series circuit.

What is Voltage?

• Voltage across a component measures the energy transferred by that component.
• A voltmeter, connected in parallel measures voltage.
• The units for voltage are volts (V).
• Potential difference is another term for voltage.
• It is the amount of energy transferred between two points in a circuit.
• A higher voltage indicates that more energy is being transferred.

Voltage in Circuits

• In a series circuit, the voltages across all components add up to the voltage across the cell.
• In a parallel circuit, the voltage across each branch is the same as the voltage provided by the cell.
• Series circuit experimental data: the voltage is shared between the components.
• For instance, in a circuit powered by 9V, voltmeters V2 and V3 might each read 4.5V.
• Parallel wiring experimental data: the voltage remains the same across all branches.
• For instance, if position V1 has a recorded voltage of 9V, V2 and V3 would also record 9V.

Brightness and Bulbs

• Adding more light bulbs in series dims the brightness of the lightbulbs.
• Adding more light bulbs in parallel does not change the brightness of the light bulbs.