M. Rahman P1 TOPIC 5 1)Electric Current is a… a)A flow of energy around a circuit b) A flow of negative charge around a circuit c) A flow of positive charge around a circuit Answer A flow of negative charge around a circuit

M. Rahman P1 TOPIC 5 2) Voltage is a measure of… a)Current b) Charge c) Energy transferred Answer C) Energy transferred

M. Rahman P1 TOPIC 5 3) Describe what an AC current is. Answer Alternating current Keeps changing direction

M. Rahman P1 TOPIC 5 4) Name some sources of AC current. Answer Mains electricity –homes Generators

M. Rahman P1 TOPIC 5 5) Describe what a DC current is. Answer. Direct Current Flows in the same direction

M. Rahman P1 TOPIC 5 6) Name some sources of DC current. Answer Batteries Solar cell

M. Rahman P1 TOPIC 5 7) What is electrical power? a) Voltage transferred per second b) Current transferred per second c) Energy transferred per second Answer. c) Energy transferred per second P = Energy/Time It tells you how quickly energy is transferred..

M. Rahman P1 TOPIC 5 8) How is power calculated from current and voltage? Answer Power = current X voltage P= I X V

M. Rahman P1 TOPIC 5 9) What are the units for a) power, b) current c) Voltage? Answer a)Power= watts b) Current= amps c) Voltage= volts

M. Rahman P1 TOPIC 5 10) Describe how a current is induced (created) by moving magnet in a coil. Answer. As you move the magnet; the magnetic field through the coil changes. this change in magnetic field induces (creates) a voltage, and current flows in the wire.

M. Rahman P1 TOPIC 5 11) What happens when you reverse the magnets north-south polarity? a)Makes no difference to the direction of the induced current and voltage. b)Current and voltage are induced in the opposite direction. Answer. b) Current and voltage are induced in the opposite direction.

M. Rahman P1 TOPIC 5 12) What are the four factors that affect the size of the induced voltage and current? Answer. 1.Strength of the magnet 2.The area of the coil 3.The number of turns on the coil 4.The speed of the movement

M. Rahman P1 TOPIC 5 13) How does generators work? (3) Answer They generate AC current; by rotating a magnet or rotate a coil and keeping the magnet fixed.

M. Rahman P1 TOPIC 5 14) How is the coil rotated in; a)Fossil fuel power station? b) In hydroelectricity ? Answer a)In fossil fuel power stations, heat from burning fossil fuels causes water to be converted into steam- steam does the turning. b) Water (held behind a damn) turns a turbine which turns a generator.

M. Rahman P1 TOPIC 5 15) How is a dynamo different from a generator? (3). Answer Dynamos are specific type of generators. The magnet is rotated instead of the coil Used in bikes to power the lights. Its attached to the wheels.

M. Rahman P1 TOPIC 5 16) Name four types of non-renewable energy sources. Answer. Coal (fossil fuels) Oil (fossil fuels) Natural gas (fossil fuels) Nuclear-from uranium

M. Rahman P1 TOPIC 5 17). List some environmental problems with fossil fuels. Answer Release CO 2 -leads to global warming. Releases SO 2, leads to acid rain. Coal mining makes mess of landscapes. Oil spillage- effects marine organisms

M. Rahman P1 TOPIC 5 18) What are the problems with nuclear energy (3) Answer. Nuclear power creates radioactive waste and is difficult to dispose of. Overall cost of setting up and decommissioning nuclear power stations are really high. Always carries risks of major catastrophes.

M. Rahman P1 TOPIC 5 19) Describe some advantages of nuclear power. Answer. Its clean so does not produce CO 2 or SO 2. It produces much more energy then the same amount of fossil fuels.

M. Rahman P1 TOPIC 5 20) How do fossil fuel power stations use steam to generate electricity? (4) Answer. Fossil fuels contain chemical energy, They are burnt to produce heat energy. Heat energy boils water to produce steam Steam (kinetic energy) now turns a turbine. The turbine turns a generator, which generates electricity.

M. Rahman P1 TOPIC 5 21) How do nuclear power stations work compared to fossil fuel power stations? Answer. Instead of burning fossil fuel to produce heat;.nuclear reactors use nuclear reactions (fission) in the uranium to produce heat.

M. Rahman P1 TOPIC 5 22) What is the difference between renewable and non-renewable energy sources? Answer. Non-renewable –will run out one day and cannot be replaced. Renewable –will not run out and can be replaced.

M. Rahman P1 TOPIC 5 23) Name the seven types of renewable energy sources. Answer. a)Hydroelectricity b) Wave c) Tidal d) wind e) Solar f) Geothermal g) biomass

M. Rahman P1 TOPIC 5 24) Describe how Hydroelectric energy works and describe the advantages and disadvantages. Answer How it works Involves flooding a valley and keeping the water back by building a dam. Water caught is allowed out through turbines – making them turn. Advantages: immediate response to electricity demands. Water released and electricity produced as and when needed. Disadvantages: Initial setup costs are high.

M. Rahman P1 TOPIC 5 25) Describe how electricity is generated from waves and describe the disadvantages. Answer How it work. Up and down motion (kinetic energy) which can be used to drive a turbine. Disadvantages: Unreliable because waves die when the wind drops. Never likely to provide energy on a large scale

M. Rahman P1 TOPIC 5 26) Describe how electricity is generated from tidal power and describe the advantages and disadvantages. Answer. How it works. Tidal barrages/dams built across river estuaries, with turbines. Advantages. It is a reliable source which has the potential to generate significant amounts of energy. Disadvantages. Only few estuaries are suitable to build tidal barrages

M. Rahman P1 TOPIC 5 27) Describe how electricity is generated from wind and describe the advantages and disadvantages. Answer How it works? Kinetic energy is provided by the wind. The winds turn the turbine, which turns the generators to produce electricity. Advantages There is no pollution. Its renewable Disadvantage Spoil the view Noisy Only works when windy, so cannot supply when there is extra demand.

M. Rahman P1 TOPIC 5 28) Describe how solar power works and describe the advantages and disadvantages? Answer How it works? Converts light energy from the sun into electrical energy directly. Direct current is produced (DC). Advantages There is no pollution. Its renewable Disadvantage Only works when the sun is out.

M. Rahman P1 TOPIC 5 29) Describe how Geothermal energy works and describe the advantages and disadvantages? Answer How it works? Water is pumped in pipes down to the hot rocks and is returned as steam to drive a generator. Advantages free energy no environmental problems Disadvantage High setup costs. Very few location options

M. Rahman P1 TOPIC 5 30) Describe how electricity from Biomass is generated and describe the advantages and disadvantages? Answer How it works? Biomass could be; farm waste; animal droppings; landfill rubbish; specially grown trees/plants Its burnt in power stations to produce steam to turn a generator. Advantages If using plants or animal waste; it can be considered carbon neutral. Renewable-most can be replaced.

M. Rahman P1 TOPIC 5 31) List some of the factors that need to be considered when setting up a power station? Answer Set up cost. Environmental issues; atmospheric pollution; visual pollution; noise pollution; disruption of wildlife and habitats. Reliability issues; most renewable energy depend on weather. Location issues.; ie wave on the coast, tidal on big river estuaries. Geothermal -only in places where there are hot rocks etc. Running and fuel costs How much power it can generate

M. Rahman P1 TOPIC 5 32)What is the national grid? Answer. It is a network of pylons, cables that takes electricity from power stations to homes and industry.

M. Rahman P1 TOPIC 5 33) The electricity is transmitted as high voltage and not high current, why? Answer. High current causes the cables to heat up and a lot of energy is wasted as heat.

M. Rahman P1 TOPIC 5 34) What is the role of transformers in the national grid? Answer. To step up alternating voltage at one end and step down voltage at the other end.

M. Rahman P1 TOPIC 5 35) Why is it necessary to step up and step down voltage? Answer. Needs to be stepped up to make transmission efficient and reduce energy loss. Step down at the other end so its down to a safe and usable level.

M. Rahman P1 TOPIC 5 36) What is a transformer made from? Answer. Two coils (the primary and secondary), joined with an iron core

M. Rahman P1 TOPIC 5 37) How does a step up transformer work? Answer. They have more coils in the secondary coil then the primary, The voltage is stepped up (increased).

M. Rahman P1 TOPIC 5 38) How does a step down transformer work? Answer. They have more coils in the primary coil then the secondary, The voltage is stepped down (decreased).

M. Rahman P1 TOPIC 5 39) What is the transformer equation? Answer. Vp = Np Vs Ns Or Vs = Ns Vp Np

M. Rahman P1 TOPIC 5 40) Calculation: A transformer has 1000 turns on its primary coil and 3000 turns on its secondary. 30 V is applied across the primary coil. What is its output voltage? Answer. Vs = Ns Vp Np

M. Rahman P1 TOPIC 5 41) Calculation: A transformer has 3800 turns on its primary and 100 turns on its secondary coil. Its output voltage is 6 V. What is its input voltage? Answer. Vp = Np Vs Ns V

M. Rahman P1 TOPIC 5 42) What are risks of transmitting in very high voltage? Answer. Risks to people, eg. Flying a kite into power lines. Links between leukaemia and living near power lines.

M. Rahman P1 TOPIC 5 43) Explain what you understand by pay back; giving an example? Answer. Example loft insulation-which cost money. But you save money on heating bills. Eventually, the money you save on heating bills will equal the initial cost of insulation. Payback time is time in years it will take to get back your initial/installation cost. Payback time (years) = initial cost/annual saving

M. Rahman P1 TOPIC 5 44) Calculation. (Payback time). Draught proofing cost £100 to install. The annual saving from heating costs is £15. What is the payback time? Answer. Payback time (years) = initial cost/annual saving. £100/£15 = 7 years

M. Rahman P1 TOPIC 5 45) A wind powered generator costs £3000 to install and it produces 800 kWh of electrical energy every year. Electricity from the National Grid costs 12 p per kWh. Calculate the payback time for the wind-powered generator Answer. Annual saving = 800x0.12 = £96 Payback = initial cost/annual saving. £3000/£96

M. Rahman P1 TOPIC 5 46) John is choosing a new fridge. Fridge A costs £400 and will save her approximately 19p a day to run compared to her old fridge. Fridge B costs £325 but would only save her 13p a day to run. Which fridge will have the shorter payback time? Answer. Fridge A: annual saving= 0.19 x 365 = £69.35 Fridge A payback time = initial cost/annual saving. £400/£69.35 = 5.77 years Fridge B: annual saving= 0.13 x 365 = £47.45 Fridge B payback time = initial cost/annual saving. £325/£47.45 = 6.85 years Fridge A has the shorter payback time

M. Rahman P1 TOPIC 5 47) a) If a light bulb transfers 1,250J of energy in 25 seconds what is the power of the light bulb? b) An electric motor transfers 15,000J of energy in 20 seconds. What is its power? Answer. a) Power = Energy/time= 1,250/25= 50W b) Power = Energy/time= 15,000/20= 750W

M. Rahman P1 TOPIC 5 48 a) A light bulb has a power rating of 100W. How much energy, in kJ is transferred over 45 minutes? Answer. Power = Energy/time (Rearrange) energy= power x time 100 x (45x 60) 100 x ,000 J 270 kJ

M. Rahman P1 TOPIC 5 49) A crane has a power rating of 75kW. How much energy is transferred in half an hour? Give your answer in kJ? Answer. Power = Energy/time (Rearrange) energy= power x time (75 x 1000) X (30x 60) x ,000,000 J 135,000 KJ

M. Rahman P1 TOPIC 5 50) An electric heater has a power rating of 2KW. What is the cost of using the fire for 3 hrs if one kWh of electricity cost 12p?. Answer. cost = Power X Time X cost of 1 KW Cost = 2kW x 3h x 12p/kWh = 72p

M. Rahman P1 TOPIC 5 51) A kettle uses 45.2 kW of energy over 120 minutes. If electricity costs 10 p per unit, how much does it cost to use the kettle?. Answer. cost = Power X Time X cost of 1 KW Cost = 45.2 x 2h x 10p = 900p (120 minutes = 2 hrs)