Energy Sources (Cambridge (CIE) IGCSE Physics)

Fig.4.1 represents a hydroelectric system for generating electrical energy.

Describe how the power station uses the water in the reservoir to generate electricity.

State three advantages of generating electricity using a hydroelectric system compared with using a coal-fired power station.

An electric drill is shown in Fig.4.2. 

Complete the sentences about the electric drill. Use words from the box. Each word may be used once, more than once, or not at all.

(i) Energy is transferred electrically from the mains supply to the ............................. store of the drill. 

[1]

(ii) A second electric drill transfers the same amount of energy per second as the first one. However, it wastes more of this energy.The second drill is less ......................................... than the first drill.[1]

Fig. 5.1 shows a wind turbine.

Describe how the wind turbine produces electricity.

Wind turbines are used in many countries to replace coal-fired power stations.

(i) State one disadvantage of using wind turbines compared to coal-fired power stations.

[1]

(ii) State two advantages of using wind turbines instead of coal-fired power stations.

[2]

A tidal barrage (dam) produces electricity using tides. Fig. 5.1 shows a diagram of a tidal barrage (simplified).

The water behind the barrage (dam) has most of its energy in one of its energy stores. State the name of this energy store.

Explain how the tidal barrage (dam) produces electricity.

Fig. 5.1 shows a geothermal power station. It generates electricity.

In a geothermal power station, the process of generating electricity includes seven stages.

Four of the stages are shown below.

P   steam turns a turbine

Q   hot underground rocks heat the cold water

R   the turbine spins a generator

S    hot water rises to the surface

The flow chart in Fig. 5.2 shows the seven stages, but it is incomplete. Complete the flow chart by adding the letters P, Q, R and S in the correct sequence.

The cost of electricity obtained from a geothermal power station is similar to the cost of electricity obtained from wind turbines.

  Describe one advantage and one disadvantage of using a geothermal power station to generate electricity compared with using wind turbines.

Nuclear fission is used in nuclear power stations to release energy.

Describe how the energy is used to generate electricity.

Describe two environmental problems that arise from using nuclear power stations.

Extended tier only

A solar panel receives energy from the Sun at a rate of 5.0 kW.

Thermal energy is transferred from the solar panel to water with an efficiency of 20%.

Cold water of mass 15 kg enters the solar panel every hour.

 The specific heat capacity of water is 4200 J / (kg°C).

 Calculate the temperature increase of the water.

temperature increase = .....................................................°C 

State and explain one advantage and one disadvantage of heating the water in a solar panel compared with heating the water in a coal-burning boiler.

Energy sources used to generate electricity are shown in the box.

Which energy sources are non-renewable?

 Draw a ring around each energy source that is non-renewable.

The diagram shows a geothermal power station.

Describe how the geothermal power station generates electricity.

In America, it is estimated that tidal power costs $150 per MWh, whereas coal costs $60 per MWh. This is partly due to construction costs of the turbines for tidal power. 

Suggest why it is expensive to construct tidal turbines. 

Extended tier only

Fusion is occurring in the centre of a star. The region in which a certain type of fusion is occurring has a diameter of 150 000 km.

Calculate the surface area of this sphere. 

The weight of the star around the core exerts a large force on the core. 

The core experiences a pressure of 26.5 × 10¹⁵ Pa.

(i) Calculate the size of the force due to gravity experienced by the core.

[3]  

(ii) The volume of the core is approximately constant, so pressure and temperature (in degrees Kelvin) can be approximated as directly proportional. They are related in the following equation:

c is a constant equal to 2.2 × 10⁹ Pa/K

Calculate the temperature of the core of the star. 

[2]

Extended tier only

Compare the advantages and disadvantages of nuclear fusion and nuclear fission.

Calculate the number of joules in 1 GWh.

Extended tier only

Tidal power electrically transfers energy in the kinetic store of moving water. 

When the tide is moving, a portion of sea water passes through the turbine. The turbine has a cylindrical shape as the turbine spins in a circular path. A turbine is shown in Fig. 1.1.

The cylinder is 24 m long and has a radius of 5.0 m. The tide is travelling at 6.0 m/s.

(i) Calculate the kinetic energy of this cylinder of sea water.  

Density of sea water = 1020 kg/m³

[4]

(ii) Calculate the time taken for 24 m of water to pass through the turbine at 6.0 m/s.

[1]

(iii) Calculate the power transferred to the turbine.

[1]

(iv) The turbine's electrical power output is 7.0 MW. Calculate its efficiency.

[1]

In America, it is estimated that tidal power would cost $150 per MWh produced, whereas coal only costs $60 per MWh produced. 

Suggest why tidal power is more expensive than power from fossil fuels.

Some ocean environmental groups oppose the use of tidal power, stating that it can physically harm aquatic life, as well as impacting their ability to communicate. 

Suggest why these statements could be correct.

A coal power station has an average output of 400 MW. Explain how, in a power station, burning a fuel causes a generator to produce an alternating current.

Extended tier only

The Sun has a total power output of 3.8 × 10²⁶ W across its whole surface. The surface of the Earth receives 5.0 × 10⁻⁸ % of this power. 

Calculate the total power the surface of the Earth receives from the Sun.

Extended tier only

The power that the Earth receives from the Sun is actually twice the percentage given in part (b).

(i) Suggest why the power at the Earth's surface is less than this value.

[1]

(ii) The Earth's radius is 6 370 000 m. Calculate the surface area of the Earth which is in sunlight at any one time. 

[3]

Extended tier only

(i) Under the assumption that there are no clouds obscuring the Sun, calculate the power that each square metre of the Earth receives from the Sun.

[2]

(ii) A solar cell absorbs sunlight over a surface area of 2.5 m². It has an efficiency of 0.6. Calculate its power output.

[3]

(iii) Determine the number of solar cells required to match the power output of the coal power station.

[2]