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AQA GCSE Physics Energy in systems

Energy in systems

This page covers the following topics:

An energy system is a series of objects that are able to interact with one another. There are 3 different types of energy system: open, closed and isolated.

Energy systems

Changes in energy within a system can occur when a force brings about a change in an objects speed, shape or height. Changes in energy can be calculated in a number of ways, for mechanical work it is important to understand how to calculate kinetic energy, gravitational potential energy and elastic potential energy.

Energy changes by forces

As a current flows through a wire, electrons pass through the wire and transfer energy around a circuit from an energy source to a battery. The amount of energy transferred each second (power) can be calculated with the following two different equations:

Energy changes by current

There are three ways that heat (or thermal energy) is transferred from one object to another: conduction, convection and radiation. The type of heat transfer in a system depend on the type of matter in the energy system.

Energy changes by heating

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A pot of water is boiling on a cooker as shown in the diagram, how could this be modified to create a closed energy system?

AQA GCSE Physics Energy in systems A pot of water is boiling on a cooker as shown in the diagram, how could this be modified to create a closed energy system?
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What are the useful and wasted forms of energy given off by a washing machine as it is working?

AQA GCSE Physics Energy in systems What are the useful and wasted forms of energy given off by a washing machine as it is working?
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A skydiver with a weight of 65 kg jumps from a plane, they reach a speed of 53 m/s before pulling their parachute. What is the gain of kinetic energy of the skydiver? Give your answer in kJ correct to one decimal place.

AQA GCSE Physics Energy in systems A skydiver with a weight of 65 kg jumps from a plane, they reach a speed of 53 m/s before pulling their parachute. What is the gain of kinetic energy of the skydiver? Give your answer in kJ correct to one decimal place.
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4

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A string is stretched until it is extended by 45 cm and it has a spring constant of 5 N/m. What is the elastic potential energy stored by the spring? Give your answer to 2 decimal places.

AQA GCSE Physics Energy in systems A string is stretched until it is extended by 45 cm and it has a spring constant of 5 N/m. What is the elastic potential energy stored by the spring? Give your answer to 2 decimal places.
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5

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How high is a shelf that a 1.45 kg book is put on for it to gain 18 J of gravitational potential energy? (g = 9.8 N/kg)

AQA GCSE Physics Energy in systems How high is a shelf that a 1.45 kg book is put on for it to gain 18 J of gravitational potential energy? (g = 9.8 N/kg)
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6

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A current of 4 A is flowing through a circuit which is driven by 230 V. What is the power rating of the circuit?

AQA GCSE Physics Energy in systems A current of 4 A is flowing through a circuit which is driven by 230 V. What is the power rating of the circuit?
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7

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What is the power dissipated by a current of 6 A passing through a 5 Ξ© resistor?

AQA GCSE Physics Energy in systems What is the power dissipated by a current of 6 A passing through a 5 Ξ© resistor?
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8

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Electrical power can be supplied at a high voltage with a low current, or with a low voltage and high current. Which of these combinations of current and voltage is the most efficient for transferring energy? Explain your answer.

AQA GCSE Physics Energy in systems Electrical power can be supplied at a high voltage with a low current, or with a low voltage and high current. Which of these combinations of current and voltage is the most efficient for transferring energy? Explain your answer.
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9

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In most examples of double glazing windows two panes of glass envelope an air gap, rather than having two pieces of glass stuck together. Suggest why this is good for heat insulation.

AQA GCSE Physics Energy in systems In most examples of double glazing windows two panes of glass envelope an air gap, rather than having two pieces of glass stuck together. Suggest why this is good for heat insulation.
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10

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A beaker of 500 g of water is at 25Β°C and is heated up to 55Β°C. The specific heat capacity of water is 4200 J/kgΒ°C. What is the change in thermal energy of the water for this change in temperature? Give your answer in kJ correct to one decimal place.

AQA GCSE Physics Energy in systems A beaker of 500 g of water is at 25Β°C and is heated up to 55Β°C. The specific heat capacity of water is 4200 J/kgΒ°C. What is the change in thermal energy of the water for this change in temperature? Give your answer in kJ correct to one decimal place.
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