NCEA Level 2 Electricity Practice Exam

In a parallel circuit, the total resistance is calculated using the formula that involves the sum of the inverses of each individual resistance. This approach arises from the nature of parallel circuits, where the voltage across each component remains the same, and the overall current is the sum of the individual currents through each resistor.

When resistors are connected in parallel, they provide multiple paths for current to flow, which effectively reduces the total resistance of the circuit compared to the resistance of any single path. Therefore, the total resistance can be found by taking the reciprocal of the sum of the reciprocals of each resistance value. Mathematically, this is expressed as:

1/R_total = 1/R_1 + 1/R_2 + 1/R_3 + ...

To find the total resistance from this equation, you would then take the reciprocal of the sum of the inverses, resulting in:

R_total = 1 / ( (1/R_1) + (1/R_2) + (1/R_3) + ... )

This process illustrates how adding more resistors in parallel decreases the total resistance, as opposed to a series circuit where total resistance simply increases with the addition of more resistors.

Other methods, such as simply summing