Current and Voltage in Circuits

Understanding Electric Current

• The electric current (I) is a flow of electric charges. It is measured in Amperes (A).
• The current in a series circuit is the same at all points, but for parallel circuits, the current is split between the branches.
• The direction of the current is taken as the direction in which positive charges flow, from the positive terminal (+) to the negative terminal (-) of a power source, such as a battery.
• Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points, which can be written as `I = V/R`, where V is the voltage and R is the resistance.

Voltage in a Circuit

• The voltage (V) also known as potential difference, is the energy transferred per unit charge. It is measured in Volts (V).
• In a series circuit, the voltage is shared among components, whereas in a parallel circuit the voltage is the same across each component.
• The voltage of an electric circuit can be measured using a voltmeter, which must be connected in parallel to the component.
• Take note that the Energy Provided by the power supply equals the energy transferred by the components, which is denoted as `Power supply voltage = sum of the component voltages`

Analysing Circuit Diagrams

• A series circuit has only one path for the electric current to follow. This means all components are consecutive.
• A parallel circuit has more than one path for the electric current to follow. This means some components are connected side by side.
• Common components in a circuit include resistors, bulbs, ammeters and voltmeters. Each has its own symbol in a circuit diagram.
• Remember to decipher circuit diagrams, using the layout and symbols to comprehend the circuit structure and its components.

The Role of Resistance in Circuits

• Resistance (Ω) is the opposition to the current flow in an electric circuit. It’s influenced by the material, temperature, length and cross-sectional area of the component.
• Resistance can be calculated using the formula `R = V/I`, where V is voltage and I is the current.
• In a series circuit, the total resistance is the sum of the resistances, whereas in a parallel circuit the total resistance is given by `1/Rtotal = 1/R1 + 1/R2 + …`
• The resistor is a common circuit component used to regulate the current in an electric circuit.

Note: Understanding how current and voltage work in different circuit conditions is fundamental for comprehending more complex electronics and solving related problems. Remember Ohm’s Law and practise using it to calculate unknown quantities in circuit questions.