1 (b) (i) 0.2 (V) accept any value between 0.20 and 0.21 inclusive 1 (ii) 37.5 allow 1 mark for I = 0.008 or allow 2 marks for correct substitution, ie 0.3 = 0.008 × R or allow 1 mark for a correct substitution using I = 0.8 or I = 0.08 or I = 0.009 or allow 2 marks for answers of 0.375 or 3.75 or 33(.3) 3 (c) (i) 25 1 mark for obtaining period = 0.04(s) 2 (ii) diode has large resistance in reverse / one direction 1 so stops current flow in that / one direction allow diodes only let current flow one way / direction allow 1 mark for the diode has half-rectified the (a.c. power) supply 1 [12] M9.(a) (i) 50(Hz) ignore any unit given 1 (ii) any two from: (some) current flows to Earth • accept ground for current flows through copper braid • accept current flows through the earth wire
1 (b) (i) 0.2 (V) accept any value between 0.20 and 0.21 inclusive 1 (ii) 37.5 allow 1 mark for I = 0.008 or allow 2 marks for correct substitution, ie 0.3 = 0.008 × R or allow 1 mark for a correct substitution using I = 0.8 or I = 0.08 or I = 0.009 or allow 2 marks for answers of 0.375 or 3.75 or 33(.3) 3 (c) (i) 25 1 mark for obtaining period = 0.04(s) 2 (ii) diode has large resistance in reverse / one direction 1 so stops current flow in that / one direction allow diodes only let current flow one way / direction allow 1 mark for the diode has half-rectified the (a.c. power) supply 1 [12] M9.(a) (i) 50(Hz) ignore any unit given 1 (ii) any two from: • (some) current flows to Earth accept ground for • current flows through copper braid accept current flows through the earth wire