9 Marking scheme: Worksheet (AS)
1 B                                                                                                            [1]
 2 C                                                                                                            [1]
 3 D                                                                                                            [1]
 4 D                                                                                                            [1]
 5 B                                                                                                            [1]
 6 The two units are: V m–1                                                                                     [1]
   and N C–1.                                                                                                   [1]
         F     1.5 × 10 −3
 7 E=       =                                                                                                   [1]
         Q     5.0 × 10 −8
    E = 3.0 × 104 V m–1                                                                                         [1]
 8 F = EQ = 5.0 × 105 × 3.2 × 10–19                                                                             [1]
   F = 1.6 × 10–13 N                                                                                            [1]
          V         600
 9 a     E=   =                                                                                                 [1]
           d     3.0 × 10 − 2
      E = 2.0 × 104 V m–1                                                                                       [1]
      The field acts towards the negative plate.                                                                [1]
    b The electric field is uniform between the plates (except at the ‘edges’).                                 [1]
      The electric field is at right angles to the plate.                                                       [1]
    c i                                                   Since the droplet is stationary,
                                                          the electric force on the droplet
                                                          must be equal and opposite to its weight.             [1]
                                                          The electric force must act upwards,
                                                          so the charge on the droplet must
                                                          be negative.                                          [1]
                    F
         ii E =
                    Q
                   F     6.4 × 10 −15
              Q=      =                                                                                         [1]
                   E      2.0 × 10 4
              Q = 3.2 × 10–19 C                                                                                 [1]
10 a  F = QE =1.60 × 10–19 × 2.4 × 106                                                                          [1]
      F = 3.84 × 10−13 N ≈ 3.8 × 10−13 N                                                                        [1]
                        F
    b F = ma ⇒ a =                                                                                              [1]
                        m
                    −13
          3.84 × 10
      a=                 N
          1.67 × 10 − 27
      a = 2.30 × 1014 m s−2                                                                                     [1]
    c Zero; the force is at right angles to the field.                                                          [1]
AS and A Level Physics                                    Original material © Cambridge University Press 2010     1
                                                           9 Marking scheme: Worksheet (AS)
              V     200
11        E=     =       × 10−2 = 4.0 × 103 N                                                         [1]
              d      5
                          F     3.2 × 10−4
          F = EQ ⇒ Q =       =                                                                        [1]
                          E      4.0 × 103
          Q = 8.0 × 10−8 C                                                                            [1]
AS and A Level Physics                          Original material © Cambridge University Press 2010     2