Edexcel IGCSE Physics C Energy and Voltage in Circuits Questions

electron(s);

allow ion(s), cation(s), anion(s)

energy (transferred) per unit charge (passed);

allow V=E / Q only if all terms
defined
allow work done for energy
transferred
allow coulomb for unit charge

- any attempt to add any currents together
- current = 39 mA

Marking guidance:
- 60, 65, or 82 mA scores 1 mark.

- components are connected in series
- voltages must add up to 6.0 V

Accept:
- voltages must add up to battery voltage
- 6.0 - 3.9 = 2.1

Ignore:
- voltmeter is in parallel with the resistor

Marking points:
- correct substitution into $V=I\times R$
- rearrangement
- evaluation

Example:
$$2.1=I\times290$$$$I=\frac{2.1}{290}$$$$I=0.0072\ \mathrm{A}$$

Accept:
- ECF from incorrect voltage
- $0.0206\ldots\ \mathrm{A}$ or $0.0134\ldots\ \mathrm{A}$ scores 2 marks
- $0.007\ \mathrm{A}$ or $0.00724\ldots\ \mathrm{A}$

same answer as 3(a)(ii)

Expected:
- 0.0072 A

Accept:
- rounded differently from 3(a)(ii), but still consistent

Marking points:
- correct substitution into $V=I\times R$
- rearrangement
- evaluation

Example:
$$3.9=0.0072\times R$$$$R=\frac{3.9}{0.0072}$$$$R=540\ \Omega$$

Accept:
- ECF from current in part (ii) or part (iii)
- 557, 542, $541.6\ldots$, 539, or $538.5\ldots\ \Omega$

Marking guidance:
- allow dimensionally correct rearrangement using incorrect voltage for the rearrangement mark only, e.g. R=2.1/0.0072

thermistor/circuit resistance decreases (as temperature increases);
current increases;
resistance of resistor is fixed/does not change AND V=IR (so voltmeter reading increases);
allow idea of less
voltage across
thermistor
allow idea that battery/total voltage is fixed/6V AND this is shared between thermistor and resistor
(so voltmeter reading
increases)

any three from:

MP1. place thermistor (and thermometer) into beaker of water;

MP2. idea of varying temperature of water / thermistor;

MP3. measure reading on voltmeter (at different temperatures);

MP4. plot graph of voltmeter reading against temperature;

MP5. idea of using graph to read off temperature at different voltmeter readings;

ignore methods involving adding bulbs to circuit etc. can be awarded from diagram

allow idea of measuring current or calculating resistance (at different temperatures)

allow current / resistance for voltmeter reading

allow current / resistance for voltmeter reading

larger current means larger voltage across fixed resistor;
total voltage remains constant;

charge = current x time

Accept:
- standard symbols and rearrangements, e.g. Q = I x t

Reject:
- use of C/c for charge or current

Marking points:
- substitution
- rearrangement
- evaluation

Example:
$$-9.4\times10^{-9}=\text{current}\times12$$$$\text{current}=\frac{-9.4\times10^{-9}}{12}$$$$\text{current}=-7.8\times10^{-10}\ \mathrm{A}$$

Accept:
- $7.83\ldots\times10^{-10}\ \mathrm{A}$

Marking guidance:
- power-of-ten error gives a 1 mark penalty