Electric circuits and components

Learning objectives

Draw and interpret circuit diagrams using standard symbols for cells, batteries, power supplies, switches, fixed and variable resistors, lamps, heaters, thermistors, LDRs, relays, fuses, ammeters and voltmeters, and at Extended diodes and LEDs

Know that in a series circuit the current is the same at every point and the resistances add, using R = R₁ + R₂, and at Extended that the p.d.s across the components add up to the supply p.d.

Know that in a parallel circuit the current from the supply is larger than the current in any branch and the combined resistance is less than either branch, explain the advantages of parallel wiring for lamps, and at Extended know that the p.d. across each branch is the same and the branch currents add up to the supply current, and use 1/R = 1/R₁ + 1/R₂

Describe the action of a variable potential divider, and at Extended use V₁/V₂ = R₁/R₂ for two resistors in series

Describe how the resistance of an NTC thermistor falls as temperature rises and that of an LDR falls as light intensity rises, and use them in sensing circuits

Describe the action of a relay as a switch operated by a small current and, at Extended, of a diode as allowing current in one direction only