1. Data analysis question.A student sets up a circuit to study the variation of resistance R of a negative temperature coefficient (NTC) thermistor with temperature T. The data are shown plotted on the graph.

(a) Draw the best-fit line for the data points.

(b) (i) Calculate the gradient of the graph when T=291 K.

(ii) State the unit for your answer to (b)(i).

(c) The uncertainty in the resistance value is 5%. The uncertainty in the temperature is negligible. On the graph, draw error bars for the data point at T=283K and for the data point at T=319K.

(d) The electric current through the thermistor for T=283K is 0.78 mA. The uncertainty in the electric current is 0.01 mA.

  • (i) Calculate the power dissipated by the thermistor at T=283K.
  • (ii) Determine the uncertainty in the power dissipated by the thermistor at T=283K.

2. This question is about the internal resistance of a cell.

(a) Define electromotive force (emf ).

(b) A circuit is used to determine the internal resistance and emf of a cell. It consists of the cell, a variable resistor, an ideal ammeter and an ideal voltmeter. The diagram shows part of the circuit with the ammeter and voltmeter missing.

The variable resistor is set to 1.5Ω. When the cell converts 7.2 mJ of energy,5.8 mC of charge moves completely around the circuit. The potential difference across the variable resistor is 0.55 V.

  • (i) Draw on the diagram the positions of the ammeter and voltmeter. [1]
  • (ii) Show that the emf of the cell is 1.25 V.
  • (iii) Determine the internal resistance of the cell.

(iv) Calculate the energy dissipated per second in the variable resistor.


3. This question is about radioactive decay.A nucleus of an iodine isotope, I-131, undergoes radioactive decay to form a nucleus of the nuclide xenon-131. Xe-131 is stable.

(a) Explain what is meant by an isotope.

(b) Identify the missing entries to complete the nuclear reaction for the decay of I-131.

(c) The initial activity of a sample of I-131 is 100 kBq. The subsequent variation of the activity of the sample with time is shown in the graph.

(i) The I-131 can be used for a medical application but only when the activity lies within the range of (20 ± 10) kBq. Determine an estimate for the time during which the iodine can be used.

(ii) A different isotope has half the initial activity and double the half-life of I-131. On the graph in (c), sketch the variation of activity with time for this isotope.




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