Physics·Electricity and magnetism · NSSCO 5.3
Series & parallel circuits
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There are only two ways to join components together — in series or in parallel — and everything about a circuit follows from which one you choose. In this lesson we learn the circuit symbols, draw both kinds of circuit, and master the three golden rules for each: how the current behaves, how the voltage (p.d.) shares out, and how to add up the total resistance (series R = R₁ + R₂ + …; parallel 1/R = 1/R₁ + 1/R₂ + …). Worked examples all the way.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 5.3):
- Draw circuit diagrams using the standard symbols for cells, batteries, switches, fixed and variable resistors, lamps, ammeters, voltmeters, fuses and relays
- State and use the rule that the current is the same at every point in a series circuit
- State and use the rule that the current from the source is the sum of the currents in the branches of a parallel circuit
- State and use the rule that the p.d.s across components in series add up to the supply p.d.
- State that the p.d. is the same across each branch of a parallel circuit
- Recall and use R = R₁ + R₂ + … for resistors in series, and 1/R = 1/R₁ + 1/R₂ + … for resistors in parallel (which is less than the smallest resistor)
- Explain the effect of arranging cells in series and in parallel, and state the uses of variable resistors, fuses and relays
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.