Answers to KS3 level 7 questions

28. (a) circuit A if more than one letter is given
award no mark 1

(b) smaller or lower accept ‘half’ 1

any one from 1

· because the resistance is larger accept ‘the resistance is smaller in E’

· because the current has to flow accept ‘because there are more bulbs’
through more bulbs

do not accept ‘because two bulbs use up more energy’ or ‘because the current is less’

If the two bulbs are in parallel, then the ammeter must be in one of the branches of the circuit e.g.

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29. (a) increases accept ‘more gets flattened’ 1
or ‘gets bigger or larger’

(b) increases accept ‘more gets flattened’ 1
or ‘gets bigger or larger’

(d) 40 1

0.5 accept ’30 minutes’ 1

140 1

(e) the speed of the car probably varies accept ‘it stops and starts’ 1
or ‘it goes faster and slower’

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30. (a) (i) red do not accept ‘pink’ or ‘pinky red’ 1

(ii) red accept ‘dark red’ 1

(b) (i) black do not accept ‘green’ or ‘brown’
or ‘browny black’ 1

or ‘dark colour’

(ii) any one from 1

· red ink absorbs green light

· red ink only reflects red light

· no green light is reflected from the ink

accept ‘no light is reflected’

accept ‘there is no red light in green’

do not accept ‘there is no red in green’

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31. (a) (i) to produce a magnetic field accept ‘to make the iron or core or 1
or make an electromagnet it magnetic’ or ‘to make a magnet’

do not accept ‘to conduct the current’

(ii) any one from 1

· to make the magnetic field stronger

· to make the electromagnet stronger

accept ‘to focus or carry the field lines’

do not accept ‘to make an electromagnet’ or ‘to make the electromagnet better’

(b) it is magnetic answers may be in either order 1

it conducts electricity accept ‘it is attracted to the coil 1
or core or electromagnet’

accept ‘it conducts’

· the electromagnet overcomes accept ‘the pull of the electromagnet
the springy metal becomes more than the pull of the spring

· the moment of the electromagnet’s
force is bigger than the moment
of the spring’s force

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32. (a) (i) any one from 1

· attracted to the accept ‘attracted’
electromagnet or ‘sticks to the electromagnet’

· bends towards the accept ‘moves left’ or ‘bends in’ or ‘bends’
electromagnet do not accept ‘vibrates’ or ‘makes a noise’

or ‘becomes magnetised’ without qualification

(ii) Any one From 1

· goes back to where it was accept ‘ not attracted any more’
or returns to normal’

· springs back

· bends back

· it straightens

do not accept ‘nothing’ or ‘it stops vibrating’

(iii) any one from 1

· none or no difference do not accept ‘bends the other way’

· it would still attract

(b) (i) higher pitch accept ‘higher’ 1

if both higher and louder given award no mark

because the frequency accept ‘because the steel sheet vibrates 1
of the vibration increases faster or moves faster’

do not accept ‘it vibrates more’

(ii) any one from 1

· larger amplitude accept ‘bigger vibrations’ or ‘larger
vibrations amplitude’ or ‘more energy’

do not accept ‘it vibrates more’

· sheet would bend more
or further

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33. (a) (i) 40 1

(ii) 1.6 consequential marking applies 1

accept answer (a) (i) ¸ 25

(b) 1.5 km/min accept ‘4 min = h’ or ‘0.067h’ 1

1.5 × 60 = 90 accept ‘6 ¸ = 90’ or ‘6 ¸ 0.067 = 90’ 1

award both marks for a correct answer even if no working is shown

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34. (a) (i) the spark accept ‘the sparkler’ 1

(ii) the glass of water accept ‘the glass’ or ‘the water’ 1

(iii) the poker 1

(b) any one from 1

· energy transferred to beaker accept ‘thermal energy is lost to the beaker
or air or surroundings or air or room’ or ‘it has been dissipated’

· beaker or air has been warmed up

· surroundings have warmed up

accept ‘used or lost during evaporation’ or ‘used to form steam’

accept ‘lost as heat’ or ‘lost as sound’

do not accept ‘lost’

do not accept ‘evaporation’

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35. (a) one mark is for the correct value and the other mark is for the corresponding unit

either

· 1500 accept ‘100 × 15’ 1

· N cm or newton cm 1

· 15 accept ‘100 × 0.15’

· N m or newton metre

(b) exert a larger force answers maybe in either order 1

accept ‘use a bigger force’ or ‘push harder’

do not accept ‘exert a larger pressure’

         exert the force further away from       accept ‘push down further from the nut’ 1
the nut                                               or ‘exert the force further along the
                                                         spanner’

do not accept ‘use of a longer spanner’

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36. (a) 40 accept ‘50 × 0.8' unless followed 1

by an incorrect answer

N m accept 'mN' 1

accept '4000 N cm' for both marks

(b) 12.5 accept ‘0.5 ¸ 0.04' unless followed 1

by an incorrect answer

m/s or m s–1 accept '1250 cm/s' for both marks 1

do not accept 'half’ or ‘weaker'

the same as or equal to accept 'same' 1

do not accept 'similar'

(d) 250 Hz if more than one box is ticked, 1

award no mark

(e) answers must be given in a logical sequence to gain full marks. Answers
must refer to energy changes and not merely list a sequence of events

any three from 3

·   chemical energy in the bell-ringer   accept 'potential energy in the bell-ringer
                                                    'or 'chemical energy'
                                                    do not accept ‘energy in the bell-ringer'

· transferred via the rope or accept 'transferred from the rope'
transferred mechanically or ‘to the rope'

·   transferred to the bell                     accept 'potential energy or kinetic
                                                    energy in the bell'
                                                    do not accept ‘to kinetic energy'
                                                    or 'to potential energy 'without a
                                                    reference to the bell or clapper

· as the bell swings, kinetic energy a reference to the bell swinging
changes to potential energy or is required for this mark
potential energy changes
to kinetic energy

· transferred by sound or accept ‘to sound' or ‘to people's
becomes sound energy or ears' or 'to the air'
transferred to the surroundings

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37. (a) (i) iron 1

(ii) iron or steel 1

(b) (i) any three from 3

· current flows in the coil do not accept ‘the circuit is completed'

· the core becomes accept ‘the coil becomes an electromagnet'
magnetised or 'the electromagnet is turned on'

· the armature is attracted

· the armature pushes the do not accept ‘the contacts come together'
contacts together

(ii) the answer must show an understanding that the contacts remain closed

         because current continues         accept ‘the contacts are in parallel with 1
through the contacts or             the switch' or ‘the contacts stay shut'
because the contacts keep         do not accept ‘there is a complete circuit'
the circuit complete                   or 'the current still flows'

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38. (a) the energy had to be shared by accept 'there was more water to heat up' 1
more particles or water or 'the heat is spread out more'

do not accept ‘there was more water'

(b) A 44 both answers are required for the mark 1

B 34

any one from 1

· the block in B, because its do not accept ‘B, because there
temperature dropped by the was more water to heat up'
larger amount

· the block in B, because this block
ended up at a lower temperature

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