What analog designer hasn't had to derive a nonstandard resistor value by using series/parallel combinations of standard resistor values? In efforts to avoid a production trimpot tweak, we can use 0.1 ...

This circuit contains a 5 Ω resistor in series with two resistors, 6 Ω and 4 Ω, which are in parallel. Start by calculating the combined resistance of the two parallel resistors.

The program generally calculates several parallel combination values that fall well within 0.1% of the desired value. By comparison, a single 1% resistor's nominal value may differ by as much as 1.45% ...

Use Ohms law to relate resistance, current and voltage. In National 5 Physics calculate the resistance for combinations of resistors in series and parallel.

Designing a high-resistance-grounding system The main challenge in designing an HRG system is determining the proper ohmic value for the neutral-grounding resistor.