CIE iGCSE Co-Ordinated Science P4.3.1 Circuit diagrams and circuit components Exam Style Questions Paper 4
Question
A student investigates an NTC thermistor.
(a) The student connects the thermistor in series with a cell and an ammeter.
The student also connects a voltmeter to measure the potential difference across the thermistor.
Fig. 3.1 shows an incomplete circuit diagram of the circuit used by the student.
(i) Complete Fig. 3.1.
(ii) When the thermistor is at room temperature, the ammeter reads 3.0A.
Calculate the charge that flows through the thermistor in 60s.
State the unit for your answer.
charge = ……………… unit ……………..
(b) The student places the thermistor into hot water.
The student records the values shown by the ammeter and the voltmeter as the temperature of the thermistor increases.
Describe how the power output of the thermistor changes as the temperature of the thermistor increases.
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(c) Fig. 3.2 shows the current–voltage characteristic for an ohmic resistor.
Explain the shape of the graph shown in Fig. 3.2.
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▶️Answer/Explanation
Ans: 3(a)(i) correct thermistor symbol in correct place ;
A and V correct ;
3(a)(ii) (Q =) It or 3 × 60 ;
(Q =) 180 ;
C/coulombs ;
3(b) resistance (of thermistor) decreases ;
current (in thermistor) increases ;
reference to P = IV;
power increases ;
3(c) straight line goes/through the origin;
Any one from:
constant resistance ;
current proportional to voltage ;
obeys Ohm’s law ;
resistance = 1 ÷ gradient ;