Energy Stores, Transfers & Conservation
Energy is stored in different ways and transferred between stores by heating, waves, electric current, or mechanical work. The principle of conservation of energy states that energy cannot be created or destroyed, allowing you to equate kinetic, gravitational potential, elastic, and thermal energy transfers and calculate device efficiency.
- Kinetic Energy
- The energy an object has due to its motion.
- Gravitational Potential Energy (GPE)
- The energy an object has due to its height in a gravitational field.
- Specific Heat Capacity
- The amount of energy required to raise the temperature of 1 kg of a substance by 1°C.
Energy Stores, Transfers & Conservation: Wave Equation (v = fλ) & Force Vector (F = ma) Simulator
Adjust physical variables on the sliders below to see real-time changes in wave geometry, resultant forces, and acceleration.
F_net = 80 N − 25 N = 55 NAcceleration: a = F_net ÷ m = 55 ÷ 10 = 5.50 m/s²Key Concepts & Exam Definitions (5)
- Kinetic Energy
- The energy an object has due to its motion.
- Gravitational Potential Energy (GPE)
- The energy an object has due to its height in a gravitational field.
- Specific Heat Capacity
- The amount of energy required to raise the temperature of 1 kg of a substance by 1°C.
- Power
- The rate at which energy is transferred or work is done, measured in Watts (W).
- Dissipation
- The process of energy being transferred to less useful stores, usually the thermal store of the surroundings.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
What is the formula for kinetic energy?
What is the unit of energy?
What happens to wasted energy?
What is the formula for gravitational potential energy?
What does 1 Watt mean in terms of energy transfer?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
Calculate the kinetic energy of a 2 kg ball moving at 3 m/s.
Click “Check Mark Scheme” to compare your answer, KE = 0.5 × 2 × (3)^2 = 9 Joules.
- Q2
A motor is supplied with 500J of electrical energy. It outputs 400J of useful kinetic energy. What is its efficiency?
Click “Check Mark Scheme” to compare your answer, Efficiency = (400 / 500) × 100 = 80%.
- Q3
Describe the energy transfers when an apple falls from a tree.
Click “Check Mark Scheme” to compare your answer, Energy is transferred mechanically from the apple's gravitational potential energy store to its kinetic energy store as it falls.
Common Exam Questions (3)
What is the principle of conservation of energy?
The principle of conservation of energy states that energy cannot be created or destroyed; it can only be transferred usefully, stored, or dissipated to the surroundings in less useful thermal stores.
What are the main energy stores?
The eight energy stores in GCSE Physics are kinetic, gravitational potential, elastic potential, thermal (internal), chemical, nuclear, magnetic, and electrostatic.
How is efficiency calculated?
Efficiency = (Useful output energy transfer ÷ Total input energy transfer) × 100%, or equivalently (Useful power output ÷ Total power input) × 100%.
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