Physics: Electricity and Magnetism - Current, Voltage, and Resistance

Electric Current ($I$): The rate of flow of electric charge ($Q$) through a conductor. It is measured in Amperes ($A$) using an ammeter connected in series.

Potential Difference or Voltage ($V$): The amount of energy or work done ($W$) per unit charge to move it between two points in a circuit. It is measured in Volts ($V$) using a voltmeter connected in parallel.

Resistance ($R$): The opposition offered by a substance to the flow of electric current. It is measured in Ohms ($\Omega$). Factors affecting resistance include length, cross-sectional area, material, and temperature.

Ohm's Law: At a constant temperature, the current ($I$) flowing through a conductor is directly proportional to the potential difference ($V$) across its ends, expressed as $V = I \times R$.

Series Circuit: Components are connected end-to-end. The current remains the same through all components ($I_{total} = I_1 = I_2$), but the total voltage is shared ($V_{total} = V_1 + V_2$).

Parallel Circuit: Components are connected across the same two points. The voltage remains the same across all branches ($V_{total} = V_1 = V_2$), but the total current is the sum of currents in each branch ($I_{total} = I_1 + I_2$).