Electromagnetism

Magentic Fields

Permanent Magnets

Mark scheme for test

1.       (a)     V = I R (stated in any correct form);
= 0.4 × 7.5;
= 3;         [Bald, correct answer scores 3 marks]                                               3

  (b)   (i)      0.2 A;                                                                                                      1

(ii)     0.8 A;                                                                                                      1

  (c)    (i)      A description to include:

1.  increases;

2.  (then) constant / levels out / stays the same / to a maximum;         2

  (ii)   temperature changes / filament hotter / due to heat;                                1

(iii)    A description to include two from:

1.  starts high / initial surge;

2.  decreases (in right context);

3.  (then) constant / levels out;                                                            2

[10]

  2.     (a)     chassis/metal casing/outer part/OWTTE;
[Allow back]
[Reject bottom/motor/door/pipes]
[Reject plastic casing]                                                                                       1

(b)     D;                                                                                                                     1

  (c)   earth; fuse; live earth;          4                                                                                                      [6]

  3.     C

[1]

  4.     (a)     (i)      A calculation to show:

·      V = IR;

V = 0.3 ´ 600;

    = 180 V;[Allow ecf]                                                                            3

  (ii)   A calculation to include:

          Either

·      P = V ´ I =180 ´ 0.3;[Allow ecf from part (i)]

·                    =54;

       or V²/R = 180²/600

·            = 54;

          or

·      I2R = 0.32 ´ 600;

·            = 54;

          [Allow 1 mark if using wrong value of resistance]                                  2

  (b)   An explanation to include:

·      will increase;

·      greater current/less resistance in circuit/greater V across blanket;

          [Allow no resistance/no resistor]
[Do not accept power by itself for second marking point]                                2

[7]

  5.     (a)     copper;
silver;                                                                                                               2

  (b)   (i)      two forces pushing outwards;
horizontal;                                                                                               2
[Reject curved lines for force]

  (ii)   An explanation to include:
          1.  positive;
          2.  like (charges) repel;                                                                   2
[Ignore poles]

  (iii)  An explanation to include:
          1.  aluminium is a conductor / OWTTE;
          2.  charge / current would flow to earth / OWTTE;                        2

  (c)    (i)      Any two correct suggestions, for example, Vander graaf /
lightning conductor / Plasma ball / photocopiers / spray painter /
precipitator (smoke cleaning) / insecticide sprays / particle accelerators / 2
inkjet printers;

  (ii)   Any two correct suggestions, for example, shocks / dust /
electronic circuit damage / hair standing on end / explosions (fuel) /
could turn pace maker off / tumble dryer / lighting;                                2

[12]

  6.     A

[1]

  7.     B

[1]

  8.     (a)     cooker;
highest power/most current;                                                                              2

  (b)   biggest current for same voltage/needs high current/
high power;                                                                                                      2
largest current with lowest resistance;

(c)     thick cables have a lower resistance;
thick cables produce less heat;                                                                         2

[6]

  9.     (i)      An explanation to include:

1.  friction between duster and comb;

2.  charge transferred in the process/ moved off / pull;                       2

          [Ignore reference to sign of charge]

  (ii)   A suggestion to include:

1.  paper contains charges / paper charged;

2.  opposite charges;

3.  attract(ed) to comb;                                                                      2

  (iii)  comb earthed / metals conduct / metals cannot be charged /
metal is not charged / charge goes to hand;                                                       1

[5]

  10.   (a)     (i)      voltages  alternating/positive and negative;
[Allow voltage changes for 1 mark]                                                        2

(ii)     (a)     -    (+)6 (V)                                                                                     1

  (b)   -    (-)6 (V)                          (Allow ecf from (A))
[Allow 6 in (B) if not awarded in (A)]                                           1

(iii)    same frequency;
reduced amplitude/smaller voltage;                                                         2

 

[6]

LED Markscheme

Continuity Testing