Energy Stores & Transfers Flashcards
(21 cards)
What happens to total energy in a closed system when energy transfers occur?
There is no net change in total energy; energy is conserved.
What is the principle of conservation of energy?
Energy cannot be created or destroyed, only transferred or stored differently.
How can you show energy transfers in diagrams?
With Sankey diagrams or labelled arrows showing input, useful output, and wasted energy.
What are ways energy in a system can change?
a) Work done by forces
b) Electrical equipment
c) Heating
What changes happen to energy stores when systems change?
Energy is transferred between kinetic, thermal, gravitational potential, elastic, etc., depending on the system.
What happens when an object is projected upwards or up a slope?
Kinetic energy is transferred to gravitational potential energy.
What happens when a moving object hits an obstacle?
Kinetic energy is transferred into thermal energy and sound.
What happens when an object is accelerated by a constant force?
Work is done on it, increasing its kinetic energy.
What happens when a vehicle slows down?
Kinetic energy is transferred to thermal energy (in brakes or surroundings).
What happens when water is boiled in an electric kettle?
Electrical energy is transferred to thermal energy in the water.
What does it mean when energy is dissipated?
It spreads out into less useful stores, often as heat.
How can efficiency be increased?
Reduce wasted energy, e.g., by using insulation or lubrication.
What is the equation for efficiency?
Efficiency = Useful energy out ÷ Total energy in
Why do mechanical processes become wasteful?
Because they often produce unwanted heat, dissipating energy.
How can unwanted energy transfer be reduced?
Using lubrication (reduce friction) or thermal insulation (reduce heat loss).
How do wall thickness and thermal conductivity affect cooling?
Thicker walls and low thermal conductivity reduce the rate of heat loss.
What is the equation for gravitational potential energy (GPE)?
ΔGPE = mass × gravitational field strength × height change
(ΔGPE = m × g × Δh)
What is the equation for kinetic energy (KE)?
KE = ½ × mass × speed²
(KE = ½ × m × v²)
What is power in physics?
The rate at which energy is transferred or work is done.
What is the equation for power?
Power = Energy transferred ÷ Time
(P = E ÷ t)
What is one watt equal to?
One joule per second (1 W = 1 J/s)
