QUESTIONSHEET 1

 

(a) (i)    0.4 A                                                                                                                                               1                                       1

 

     (ii)    0.4 A                                                                                                                                               1                                       1

 

(b) (i)    potential difference = current ´ resistance                                                                                          1                    1

              2.4 V                                                                                                                                             1                                       1

 

     (ii)    1.6 V                                                                                                                                               1                                       1

 

(c) showing all working                                                                                                                                  1                             1

          correct answer with units for total resistance: 16 W                                                                                1               1

          calculate third resistance: 6 W                                                                                                               1                           1

 

TOTAL  / 8

                                                                                                                                                                       

 

 

QUESTIONSHEET 2

 

(a) (i)    144 kJ / 144,000 J                                                                                                                             1                             1

 

     (ii)   Lost in heating the surroundings, eg the kettle itself.                                                                            1               1

 

(b) (i)    10 A                                                                                                                                                1                                       1

 

     (ii)    iron / cooker / covector heater /

            any appliance whose main purpose is producing heat                                                                           2

 

(c) (i)    2.4 ´ 20/10 = 4.80                                                                                                                             1                                  1

 

     (ii)    0.1 ´ 20 ´ 10 = 20p                                                                                                                           1                                       1

 

     (iii)     20    ´  100 = 4.17%                                                                                                                       1                                  1

            480

TOTAL  / 8

                                                                                                                                                                       


 

 

QUESTIONSHEET 3

 

(a) time = 5 ´ 3 minutes = 15 minutes = 1/4 hour                                                                                             1  
     units = 2.4 kW ´ 1/4 hour = 0.6 kWh                                         1
     cost = 0.6 ´ 8p = 4.8p                                                                                                                               1

 

(b) (i)     Power = current x voltage                                                                                                                 1

    

     (ii)    current = power/voltage = 2400 W/240 V                                                                                           1
             10 A                                                                                                                                                1

 

     (iii)   13 A                                                                                                                                                1

 

(c) If the cable/cord was damaged could be a large current                                                                              1

 

TOTAL  / 8

                                                                                                                                                                       

 

 

QUESTIONSHEET 4

 

(a) (i)           12V - 10V = 2 V                                                                                                                        1

    

     (ii)     Voltage  = current ´ resistance                                                                                                        1

 

     (iii)     2 V/1000 W                                                                         1
              0.002 A or 2 mA                                                                                                                             1

 

(b) (i)      0.008 A ´ 1000 W                                                                                                                           1
               8V                                                                                                                                                 1

              12 - 8 = 4 V                                                                                                                                    1    

                                                               

     (ii)    4 V/0.008 A                                                                                                                                   1  

              = 500 W                                                                                                                                         1

 

TOTAL  / 9

                                                                                                                                                                       

 

 

QUESTIONSHEET 5

 

 

(a) dangerous                                                                                                                                                1
     too much current may flow/overloading the circuit                                                                                      1
     causing much heat and possibly a fire                                                                                                        1

 

(b) If  fault develops circuit breaker acts more quickly than a fuse                                                                    1
     reducing the chance of electrocution.                                                                                                         1

 

TOTAL  / 5

                                                                                                                                                                       

 

 

 

 

 

 

QUESTIONSHEET 6

 

(a) (i)    High heat

            parallel connection (A to B & A to D)                                                                                                1                    1

            no connection C to D                                                                                                                        1                             1

 

            Medium heat

            Single connection A to B                                                                                                                   1                           1

            No connection C to D                                                                                                                       1                             1

 

            Low heat                                                                                                                                          

            Connection A to B                                                                                                                            1                             1

            And C to D                                                                                                                                      1                                  1

 

     (ii)    Parallel circuits each element                                                                                                             1                           1

            has same current                                                                                                                              1                             1

 

            medium heat has only one element                                                                                                     1                         1

            therefore half the heat                                                                                                                       1                             1

 

            series circuit shares current                                                                                                               1                           1

            between elements                                                                                                                             1                             1

 

TOTAL  / 12

                                                                                                                                                                       

 

 

QUESTIONSHEET 7

 

(a) (i)    3000 / 240                                                                                                                                        1                                  1

            =  12.5 amps                                                                                                                                     1                                  1

 

     (ii)    13 amps                                                                                                                                           1                                  1

 

(b) 240 / 12.5                                                                                                                                                 1                                  1

     =  19.2 ohms                                                                                                                                            1                                  1

 

(c) earth connected to case of fire                                                                                                                  1                         1

 

TOTAL  / 6

                                                                                                                                                                       


 

 

QUESTIONSHEET 8

 

(a) 5A ´ 240 V                                                                                                                                                  1                             1

     =  1200 W                                                                                                                                                                                   1

     1200 / 60                                                                                                                                                      1                                  1

     =  20                                                                                                                                                            1                      1

 


(b)                                                                                                                                                                

 

 

 

 

 

 

 


     3

 

(c) 6 ´ 15 ´ 1.2 = total units                                                                                                                           1                             1

     = 108 kWh                                                                                                                                                                           1

     Price  = 108 ´ 12 p                                                                                                                                  1                             1

     = £12.96                                                                                                                                                  1

 

TOTAL  / 10

                                                                                                                                                                       

 

 

QUESTIONSHEET 9

 

(a) voltage across coil 1  =  number of turns in coil 1

          voltage across coil 2      number of turns in coil 2                                                                                   1

 

    working                                                                                                                                                   1                                       1

    correct answer with units:  12 V                                                                                                                1                         1

 

(b) (i)    current / electric current / current flow                                                                                               1                    1

 

     (ii)    A2                                                                                                                                                   1                                  1

 

(c) (i)    low current                                                                                                                                       1                                  1

 

     (ii)    1 mark for answers which include the idea that:

            flow of current converts some electrical energy to heat energy which is lost by convection                    1                                  1

            1 mark for answers which include the idea that:

            transmitting at high voltage is more efficient than at high current.                                                         1

 

TOTAL  / 8

                                                                                                                                                                       


 

 

QUESTIONSHEET 10

 

(a) (i)    a resistor whose resistance changes with temperature.                                                                        1

 


     (ii)   

 

Resistance (kW)

 

Temperature (oC)

 
 

 

 

 

 

 

 

 

 

 


            Deduct 1 mark for each incorrectly plotted point to a maximum of 2.                                                    2                                       2

 

     (iii)   decreases / goes down                                                                                                                      1                             1

 

(b) (i)    decreases / goes down                                                                                                                      1                             1

 

     (ii)    potential difference = current ´ resistance                                                                                          1                    1

 

            0.04 mA / 0.00004 A                                                                                                                         1                             1

 

(c) Light dependent resistor (LDR)                                                                                                                 1                         1

 

TOTAL  / 8

                                                                                                                                                                       

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


QUESTIONSHEET 11

 

(a) all components present:  battery or cell,

     variable resistor, bulb and ammeter all in series,                                                                                          1

     voltmeter connected in parallel with bulb only.                                                                                            1

 

 

 

 

 

 

 

 

 


(b) (i)   

 

 

Potential

Difference (V)

 
 


           

 

 

 

 

 

 

Current (A)

 
 

 

 


            Deduct 1 mark for each incorrectly plotted point to a

            maximum of 2.                                                                                                                                  2                             2

 

     (ii)    1 V  + 0.1 V                                                                                                                                     1                                  1

 

     (iii)   resistance = potential difference

                                         current                                                                                                                1                           1

 

             5 W  + 0.5 W                                                                                                                                    1                                  1

 

     (iv)   increases                                                                                                                                          1                                  1

 

TOTAL  / 8

                                                                                                                                                                       


 

 

QUESTIONSHEET 12

 

(a) (i)     787, 748, 604, 527: 

            all correct                                                                                                                                         2                                  2

            3 correct.                                                                                                                                         1                                  1

 

     (ii)    December 1998                                                                                                                                1                                  1

 

     (iii)   Weather colder so more energy required for heating or cooking/

             nights longer so more lighting required.                                                                                              1                    1

 

(b) (i)    times (h): 0.25, 0.25, 2, 0.5, 4                                                                                                             1                           1

           kWh: 0.5, 0.175, 0.4, 0.4, 0.41                                                                                                            1                           1

           Deduct 1 mark per incorrect answer to a total of 3 marks.

 

     (ii)    18.75p                                                                                                                                              1                                       1

 

TOTAL  / 8

                                                                                                                                                                       

 

 

QUESTIONSHEET 13

 

(a) low energy bulb                                                                                                                                        1

 

(b) units = 0.15 kW ´ 1000 = 150 units

     (note the change of watt to kilowatt)                                            1
     150 ´ 8p                                                                                       1
     1200 p or £12                                                                                                                                           1

 

(c) £12 ¸ 5 = £2.40                                                                                                                                       1

 

 

TOTAL  / 5

                                                                                                                                                                       

 

 

QUESTIONSHEET 14

 

(a) 1000 W (power is measured in watt, W)                                                                                                    1

 

(b) (i)     Power = current ´ voltage                                                                                                                1

 

     (ii)    current = power/voltage = 1000 W/230 V                                 1
            4.3(5) A                                                                                                                                           1

 

(c) (i)    safety device                                                                              1
            if too much current flows, it breaks and prevents

             further current flow                                                                                                                         1

 

     (ii)   5 A (use the lowest value which will allow the device to operate normally.)                                          1

                                                                                                                                                                                        

TOTAL  / 7

                                                                                                                                                                       

 

 

QUESTIONSHEET 15

 

(a) 1100 W                                                                                                                                                    1                                  1

 

(b) (i)     Power = current ´ voltage                                                                                                               1

     (ii)     current = power/voltage = 1100 W/220 V                                                                                         1
                   5 A                                                                                                                                                1

 

(c) (i)    Voltage = current ´ resistance                                                                                                           1

 

     (ii)    resistance = voltage/current = 220 V/5 A                                                                                           1
            44 W                                                                                                                                                1

 

(d) Assume the heating element has the same resistance                                                                                     
     current = voltage/resistance = 110 V/44 W = 2.5 A                                                                                     1
     power = current ´ voltage = 2.5 A ´ 110 V = 275 W                                                                                  1
     new power = 275/1100 = 1/4 of original power                                                                                           1

 

TOTAL  / 10

                                                                                                                                                                       

 

 

QUESTIONSHEET 16

 

(a) if a short circuit occurs                                                                                                                             1                           1

     current will flow to earth                                                                                                                           1                           1

     case will not become live                                                                                                                          1                           1

 

(b) short circuit causes fuse to heat up                                                                                                            1                         1

     and melt                                                                                                                                                   1                                  1

     cutting off power                                                                                                                                      1

 

TOTAL  / 6

                                                                                                                                                                       


 

 

QUESTIONSHEET 17

 

(a) current = power/voltage = 3000 W/240 V                                                                                                  1
     12.5 A                                                                                                                                                     1

 

(b)

wire

current /A

earth

0

live

12.5

neutral

12.5

                                                                                                                                                                    3

 

(c) Very large current flows                                                                                                                           1
     in the live and earth wires                                                                                                                         1
     fuse melts and breaks, preventing further current flow.                                                                               1

 

TOTAL  / 8

                                                                                                                                                                       

 

 

QUESTIONSHEET 18

 

(a)

Wire

Name

Colour

A

NEUTRAL

BLUE

B

EARTH

GREEN AND YELLOW

C

LIVE

BROWN

                                                                                                                                                                    3                           3

 

(b) (i)       earth wire                                                                                                                                      1                                       1

 

     (ii)           since the case of the hairdryer is plastic, there are no exposed metal parts                                     1                             1
               no danger of electrocution if the live wire touches the plastic case.                                                     1

                                                                                                                                                                                              1

 

(c) Fuse protects wires                                                                                                                                  1                                  1

     high current flows & melts fuse wire                                                                                                         1                         1

     circuit breaks                                                                                                                                           1                                  1

 

TOTAL  / 9

                                                                                                                                                                       


 

 

QUESTIONSHEET 19

 

(a) kilowatt                                                                                                                                                    1                                  1

     one hour                                                                                                                                                  1                                  1

     unit                                                                                                                                                          1                                       1

 

(b) 3 600 000                                                                                                                                                1                         1

      3.6 mV                                                                                                                                                                                      1

 

(c) (i)    3 amp                                                                                                                                                                                       1

            13 amp                                                                                                                                                                                     1

            5 amp                                                                                                                                                                                       1

 

     (ii)    A    3 ´ 2 = 6 units                                                                                                                            1                             1

            B    0.1 ´ 12 = 1.2 units                                                                                                                     1                           1

            Immersion heater                                                                                                                              1                             1

 

TOTAL  / 11

                                                                                                                                                                       

 

 

QUESTIONSHEET 20

 

One mark for each of

           

current

fire

damaged

metals

melting

5 amps

melt

live                  

                  

TOTAL  / 8