PART A PART A 1 Surname Name American Academy Larnaca Year 4 Science Semester 2 Test 4 Unit P1 Universal Physics Topic 5 Electricity Friday 19 th May 2013 Part A Time: 20 minutes FORMULAE You may find the following formulae useful. wave speed = frequency × wavelength v = f × λ taken time covered distance speed wave t x v electrical power = current × potential difference P = I × V cost of electricity = power × time × cost of 1 kilowatt-hour taken time used energy power t E P % 100 device) the to supplied energy (total device) by the nsferred energy tra (useful efficiency coil secondary on turns of number coil primary on turns of number voltage secondary ltage primary vo s p s p N N V V Do not forget to include units in all your answers.
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Edexcel GCSE Science P1.5 Generation and Transmission of Electricity Test 12_13 DS
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PART A
PART A 1
Surname
Name
American Academy Larnaca
Year 4 Science
Semester 2
Test 4
Unit P1
Universal Physics
Topic 5 Electricity
Friday 19th
May 2013
Part A
Time: 20 minutes
FORMULAE
You may find the following formulae useful.
wave speed = frequency × wavelength v = f × λ
takentime
covered distancespeed wave
t
xv
electrical power = current × potential difference P = I × V
cost of electricity = power × time × cost of 1 kilowatt-hour
takentime
usedenergy power
t
EP
%100device) the tosuppliedenergy (total
device) by the nsferredenergy tra (usefulefficiency
coilsecondary on turnsofnumber
coilprimary on turnsofnumber
voltagesecondary
ltageprimary vo
s
p
s
p
N
N
V
V
Do not forget to include units in all your answers.
PART A
PART A 2
1. (a) Put a cross ( ) in the box next to the correct answer.
[1 mark]
Voltage is
A the energy
B the rate of flow of charge
C the energy per coulomb
D the rate of flow of energy
(b) Below we see a graph of the energy provided to different amounts of charge by a photovoltaic
cell working in bright light.
(i) Describe one disadvantage of using solar cells.
[1 mark]
…………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………
(ii) Use the graph to show that the voltage provided by the solar cell is 0.6V.
[2 marks]
Voltage = ………………………… V
(iii) The solar cell provides an average current of 1.5 A.
Use your answer in (ii) to calculate the power produced by the solar cell.
Don’t forget the unit.
[2 marks]
Power = …………………………
0
1
2
3
0 2 4 6
Energy
(Joules)
Charge (Coulombs)
a photovoltaic cell
PART A
PART A 3
(iv) How much energy would the solar cell give in 1 minute?
[2 marks]
Energy = ………………………… J
A solar cell generates direct current.
(v) Describe the difference between direct current and alternating current.
[2 marks]
…………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………
(vi) State why a transformer cannot be used to increase this voltage.
[1 mark]
…………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………
(c) The table shows some information about the wind-powered generator.
cost (including installation) £2500
electrical energy produced in one year 900 kWh
Electricity from the National Grid costs 15 p per kWh.
Calculate the payback time for the wind-powered generator.
[3 marks]
payback time = .............................................................................. years
Mark scheme Part A 1. (a) C (b) (i) no availability at night/cloudy days/etc. expensive to buy (ii) [V=E/Q=] 2.4/6 [or any other correct values from graph] =0.4[V] (iii) [P=IV=] 1.5x0.4 =0.6W (iv) [P=E/t => E=Pt=] 0.6x60 =36J (v) DC: current flows in one direction only AC: current flows backwards/forwards in both directions (vi) transformers only work with AC (c) 900x15p=£135 £2500/£135 = 18.5 years 2. (a) D (b) (i) 150J (ii) 50/200 =0.25 or 25% (c) black radiates heat well allowing motor to cool [more quickly]
Part B 1. (a) In graph A the current flows in both directions but in B only one direction.
(b) (i)
=825V (ii) 0.50/15 =0.033A (c) X steps up V P=IV so… …high V means certain P can be transferred with small I …small I over large distances means low energy/power losses due to heating [of air] Y steps down V lower V safer for consumers
1-2 marks states that X/Y steps up/down the voltage appreciates that this reduces energy/power losses
3-4 marks may use P=IV to reason that V↑ means I↓ and vice versa small I is reason for reduced energy/power losses high V more dangerous
(d) (i) field from underground cables is lower except for short distances [<5m] (ii) ethical 2. (a) reducing [rate of increase of] carbon emissions reducing dependence on fossil fuels etc. (b) prediction saying what will happen in future 3. (a) can be replaced (b) farmers have a large supply of animal waste (c) Two from: biomass always available wind turbines take up a lot of space wind turbines are ugly biomass generator may meet more of demand for energy than small turbine