SITEMAP   School-college Physics Notes: Electricity 5.3 Identical resistors wired in series

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Electricity section 5: 5.3 How to investigate the effect on the total resistance of a circuit by adding identical resistors together in series

Doc Brown's Physics exam study revision notes:: There are various sections to work through, after 1 they can be read and studied in any order.

5.3 How to investigate the effect on the total resistance of a circuit by adding identical resistors together in series

(a) The circuit of identical resistors wired in series

You set up a relatively simple circuit of a power supply, ammeter and one or more identical resistors, all wired in series.

You start by putting one resistor in the circuit and measuring the current flowing through it (I) and the p.d. across it (V).

Then, add a second resistor in series and remeasure the p.d. and current again.

Just repeat by adding more resistors and for each pair of readings calculate the total resistance (R = V/I).

From your recorded results plot a graph of total resistance versus number of resistors in series.

You find the graph is linear proving the rule that: Rtotal = R1 + R2 + R3 etc. for resistors wired in series.

In other words the total resistance steadily increases the more resistors you connect in series,

and you should notice that the current flowing steadily decreases as the total resistance increases.

Water flow analogy: The longer the thin pipe the greater the friction is to oppose the flow.

(b)

For comparison, the graph for wiring identical resistors, shows a negative gradient, the complete opposite effect to wiring the resistors in series.

See Part 5.5 for the comparison with resistors wired in parallel

Keywords, phrases and learning objectives for wiring identical resistors in series.

Know how to investigate effect on total resistance of circuit by adding identical resistors together in series circuit.

Be able to describe with the aid of a diagram the method and how to interpret the results with the aid of a graph.

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