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4.3.2a Series circuits

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Question 4

A student investigates a circuit containing a parallel combination of two resistors, P P\,P and QQQ, connected in series with a resistor SSS, an ammeter to measure the total circuit current, and a power supply.

The student obtains the following experimental readings:

  • Potential difference across the parallel combination of P P\,P and QQQ: VPQ=1.8 VV_{PQ} = 1.8\text{ V}VPQ​=1.8 V
  • Potential difference across resistor SSS: VS=3.6 VV_S = 3.6\text{ V}VS​=3.6 V
  • Total current in the circuit: IT=0.45 AI_T = 0.45\text{ A}IT​=0.45 A
  • Branch current through resistor PPP: IP=0.15 AI_P = 0.15\text{ A}IP​=0.15 A
  • Branch current through resistor QQQ: IQ=0.28 AI_Q = 0.28\text{ A}IQ​=0.28 A
a.

Calculate the equivalent resistance RPQR_{PQ}RPQ​ of the parallel combination. State your answer with the appropriate unit.

[2]
b.

Calculate the resistance RS R_S\,RS​ of resistor SSS.

[2]
c.

State whether the student's results support the physical suggestion that IT=IP+IQI_T = I_P + I_QIT​=IP​+IQ​. Justify your statement by comparing the numerical values.

[2]
d.

Rather than using a variable resistor, the student suggests controlling the current by swapping resistors P P\,P and Q Q\,Q with different discrete resistors. State one disadvantage of this method.

[1]
Markscheme

4.3.2a Series circuits Questions

  1. IGCSE
  2. /Physics
  3. /4.3.2a Series circuits

52 exam-style questions on CIE IGCSE Physics 4.3.2a Series circuits. Each one has a worked solution and a mark scheme showing where the marks go.

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