IB Physics HL B 5 Current and Circuits Questions

Practise IB Physics HL B.5 by solving multi-loop circuits and evaluating emf, internal resistance, power, rms quantities and measurement evidence.

Exam points

Build quantitative circuit models from charge conservation, loop energy, component laws and meter assumptions to solve multi-source series and parallel systems.
Use V–I graphs, R=ρL/A and microscopic charge-transport relationships to explain resistance, resistivity, non-ohmic behaviour and material or temperature effects.
Calculate power, energy, efficiency and heating in components and transmission systems, including rms and peak quantities where an AC waveform is specified.
Analyse real cells and power supplies with ε = I(R+r), terminal pd, internal loss, load changes and series or parallel source combinations.
Relate charge, carrier density, drift speed and current continuity to measurements in conductors, liquids and illuminated devices.
Interpret AC conversion circuits by predicting rectifier current direction, waveform shape and the smoothing effect of a capacitor.
Analyse thermistor, LDR, potentiometer and potential-divider control circuits, including comparator inputs, switching thresholds and output changes.

Covered syllabus points

B.5.1—Cells provide a source of emf B.5.2—Electrical energy sources B.5.3—Resistance B.5.4—Ohmic behaviour B.5.5—Electrical power B.5.6—Potential difference and electrical energy transfer B.5.7—Electric cells B.5.8—Circuit diagrams and conventional current B.5.9—Direct current and charge flow B.5.10—Direct and alternating current boundary B.5.11—Conservation in series and parallel circuits B.5.12—Resistance and resistivity B.5.13—Series and parallel circuits B.5.14—Emf and internal resistance B.5.15—Variable resistance

[Maximum number: 7]

(a)

A cell is connected to an ideal voltmeter, a switch S and a resistor R. The resistance of R is $4.0 \Omega$ .

When S is open the reading on the voltmeter is 12 V . When S is closed the voltmeter reads 8.0 V .

[ 3 ]

(i)

State the emf of the cell.

[ 1 ]

$12 \vee$

(ii)

Deduce the internal resistance of the cell.

[ 2 ]

I=2.0 A OR 12=I(r+4) OR 4=I r OR 8=4 I

«Correct working to get » r=2.0 « $\Omega$ »

Marking guidance:

Allow any valid method.

Allow ECF from (b)(i)

(b)

A fully charged cell of emf 6.0 V delivers a constant current of 5.0 A for a time of 0.25 hour until it is completely discharged.

The cell is then re-charged by a rectangular solar panel of dimensions $0.40 \mathrm{~m} \times 0.15 \mathrm{~m}$ at a place where the maximum intensity of sunlight is $380 \mathrm{Wm}^{-2}$ .

The overall efficiency of the re-charging process is 18 %.
Calculate the minimum time required to re-charge the cell fully.

[ 3 ]

ALTERNATIVE 1 «energy output of the panel = » VIt OR $6 \times 5 \times 0.25 \times 3600$ OR 27000 «J»

«available power = » $380 \times 0.4 \times 0.15 \times 0.18$ OR 4.1 «W»
$t=\ll \frac{27000}{4.1}=>6600<\mathrm{s} \gg$

ALTERNATIVE 2

«energy needed from Sun = » $\frac{V I t}{e f f}$ OR $\frac{6 \times 5 \times 0.25 \times 3600}{0.18}$ OR 150000 «J» « incident power=» $380 \times 0.4 \times 0.15$ OR 22.8 «W»
$t=\ll \frac{150000}{22.8}=>6600<\mathrm{S} \gg$

Marking guidance:

Allow ECF for MP3

Accept final answer in minutes (110) or hours (1.8).

(c)

Outline why research into solar cell technology is important to society.

[ 1 ]

[Maximum number: 3]

This question is in two parts. Part 1 is about solar power and climate models. Part 2 is about digital storage of data.

(a)

Distinguish, in terms of the energy changes involved, between a solar heating panel and a photovoltaic cell.

[ 2 ]

(b)

State an appropriate domestic use for a

[ 1 ]

(i)

photovoltaic cell.

[ 1 ]

[Maximum number: 6]

This question is in two parts

(a)

The plates in (c) are replaced by a cell that has an emf of 12.0 V and internal resistance $5.00 \Omega$ . A resistor of resistance R is connected in series with the cell. The energy transferred by the cell to an electron as it moves through the resistor is $1.44 \times 10^{-18} \mathrm{~J}$ .

[ 6 ]

(i)

Define resistance of a resistor.

[ 1 ]

ratio potential difference/voltage (across resistor) to current (in resistor) / $\frac{V}{I}$
with symbols defined;

(ii)

Show that the value of R is $15.0 \Omega$ .

[ 4 ]

pd across $R=\frac{1.44 \times 10^{-18}}{1.6 \times 10^{-19}}=9.00 \mathrm{~V}$ ;
pd across internal resistance $=12.0-9.00=3.00 \mathrm{~V}$ ;
current in circuit $=\frac{3.00}{5.00}=0.600 \mathrm{~A}$ ;
$R=\frac{9.00}{0.600}=15.0 \Omega$ ;

(iii)

Calculate the total power supplied by the cell.

[ 1 ]

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (i)

Question (ii)

Question (b)

Question (c)

Question 2

Question (a)

Question (b)

Question (i)

Question 3

Question (a)

Question (i)

Question (ii)

Question (iii)