Energy Stores and Transfers

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Questions and Answers

What is the formula for calculating kinetic energy?

E = ½mv² (correct)

E = mgh

E = ½ke²

E = mcΔT

Which type of energy is associated with an object's position in a gravitational field?

Thermal energy

Kinetic energy

Gravitational potential energy (correct)

Chemical potential energy

How is power defined in relation to energy transfer?

Power is the total energy in a system.

Power is the energy stored in a system.

Power is the rate of energy transferred. (correct)

Power is the amount of energy converted to matter.

What describes the opposition to the flow of current in a circuit?

Resistance (B) Signup and view all the answers

Which equation represents the relationship between gravitational potential energy lost and kinetic energy gained?

GPE lost = KE gained (A) Signup and view all the answers

What type of energy is stored in the chemical bonds of molecules?

Chemical potential energy (D) Signup and view all the answers

What does specific heat capacity measure?

Energy needed to raise 1 kg of a substance by 1°C (A) Signup and view all the answers

What is the conventional direction of current flow in a circuit?

From positive terminal to negative terminal (A) Signup and view all the answers

What describes the current in a series circuit?

It is constant throughout all components. (A) Signup and view all the answers

Which equation represents Ohm's Law?

V = IR (A) Signup and view all the answers

What type of resistor changes resistance based on temperature?

Thermistor (C) Signup and view all the answers

What happens when more resistors are added in parallel?

The total resistance decreases. (C) Signup and view all the answers

Which component carries a fluctuating voltage of around 230V?

Live wire (B) Signup and view all the answers

What is the primary function of a step-down transformer?

To decrease voltage for safer household use. (B) Signup and view all the answers

What particle is emitted during alpha radiation?

Helium nucleus (B) Signup and view all the answers

Which type of current flows back and forth?

Alternating current (AC) (A) Signup and view all the answers

What does half-life describe?

The time it takes for unstable nuclei in a sample to halve. (D) Signup and view all the answers

What process involves the combining of two light nuclei?

Nuclear fusion (B) Signup and view all the answers

What is the function of a fuse in an electrical circuit?

To melt or break the circuit if current exceeds a certain limit. (A) Signup and view all the answers

Which radiation type has the highest penetrating power?

Gamma radiation (B) Signup and view all the answers

Which equation calculates power in an electrical circuit?

P = V² / R (B) Signup and view all the answers

Study Notes

Energy stores

Energy quantifies the effects of object interactions in a system.
Total energy is conserved in a closed system; it cannot be created or destroyed, but can be converted into matter.
Energy exists in various forms: kinetic energy (KE), gravitational potential energy (GPE), elastic potential energy, thermal energy, and chemical potential energy.
KE is the energy of motion, calculated as E = ½mv², where 'm' is mass and 'v' is velocity.
GPE is energy due to an object's position, calculated as E = mgh, where 'm' is mass, 'g' is acceleration due to gravity, and 'h' is height.
Elastic potential energy is stored in stretched or compressed objects: E = ½ke², where 'k' is the spring constant and 'e' is the extension.
Thermal energy is energy from particle random motion: E = mcΔT, where 'm' is mass, 'c' is specific heat capacity, and ΔT is the temperature change.
Chemical potential energy is stored in molecular bonds.

Energy transfers

Energy transfer between objects or energy stores is necessary for system change.
Energy loss to the surroundings signifies an open system.
Work is another term for energy used.
A roller coaster at the top of a hill has GPE, no KE. As it falls, GPE converts to KE.
At the bottom, GPE lost equals KE gained.
Calculating the roller coaster's speed at the bottom using KE: v = √(2KE/m).
Alternatively, using GPE and KE directly: v = √(2gh).

Specific heat capacity & Power

Specific heat capacity (SHC) shows energy to raise 1 kg of a substance by 1°C.
Power is the rate of energy transfer, calculated as P = E/t, where 'E' is energy and 't' is time.
Power units are Watts (W), equivalent to Joules per second (J/s).
Efficiency measures useful energy output compared to total input: Efficiency = Useful energy out / Total energy in, and Efficiency = Useful power out / Total power in.

Electricity

Electricity is electron flow.
Charge movement is current.
Conventional current flows positive-to-negative, opposite electron flow.
Potential difference (PD), or voltage, shows energy transferred per Coulomb of charge.
Current is charge flow rate, measured in Amperes (A).
Resistance opposes current flow.
A resistor has constant resistance, and is "ohmic" (PD and current are directly proportional).
A filament bulb has changing resistance, "non-ohmic" (PD and current are not proportional).
Ohm's Law: V = IR.
Circuit components can be wired in series or parallel.

Series circuits

In a series circuit, the total PD is split among components.
Current is the same through all components.
Total resistance is the sum of all individual resistances.

Parallel circuits

In a parallel circuit, PD is the same across each branch.
Current is split between branches.
Adding more resistors in parallel lowers the total resistance.

Resistor types

Thermistors change resistance with temperature.
LDRs change resistance with light intensity.

Power in electrical circuits

Electrical circuit power: P = VI.
Alternative power equations from Ohm's Law: P = I²R and P = V²/R.

Direct and alternating current

Direct current (DC) flows in one direction.
Alternating current (AC) flows back and forth, used in household power.
UK AC frequency is 50 Hz.

Safety in electrical circuits

Live wire (brown) carries fluctuating voltage, average 230V.
Neutral wire (blue) has 0V potential.
Earth wire (yellow/green) connects to plug's ground pin for safety during faults.
Fuses (in live wire) melt if current exceeds limit.
Appliance current: I = P/V.

National grid

A network of power stations, cables, and transformers delivering electricity.
Transformers change voltage.
Step-up transformers increase voltage, reduce current, decrease energy loss.
Step-down transformers decrease voltage, making it suitable for homes.

Atomic structure

Atoms contain a positive nucleus, with orbiting negative electrons.
The nucleus has protons and neutrons.
Atomic number is the number of protons.
Mass number is the total protons and neutrons.
Isotopes are atoms of the same element with different neutron counts.

Radiation

Radiation is emitted particles or waves.
The electromagnetic spectrum includes all types of radiation.
Gamma radiation comes from the nucleus's excess energy.
Alpha radiation is a particle of two protons and two neutrons (Helium nucleus).
Beta radiation is a high-speed electron from neutron decay.

Radioactive decay

Unstable nuclei decay to become stable.
Alpha, beta, and gamma are decay types.
Alpha has high ionization but low penetration.
Beta has moderate ionization and penetration.
Gamma has low ionization but high penetration.

Half-life

Half-life is decay time for half the activity of a radioactive source.
Half-life is also the time for half the unstable nuclei to decay, and half the sample's mass.

Nuclear fission

Fission splits a heavy nucleus (e.g., uranium-235) into lighter nuclei.
Fission releases heat and kinetic energy.

Nuclear fusion

Fusion combines light nuclei (e.g., hydrogen) into a heavier nucleus.
Fusion releases more energy than fission.
Fusion needs high temps and pressures.

Key concepts

Energy is conserved.
Power is energy transfer rate, and efficiency measures useful energy.
Electricity is charge flow, and PD is energy per Coulomb.
Resistance opposes flow, and Ohm's Law relates PD, current, and resistance.
Circuits have series and parallel connections.
Atoms have protons, neutrons, and electrons.
Radioactive decay changes unstable nuclei.
Nuclear fission splits heavy nuclei, and nuclear fusion joins light ones.

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Description

Explore the various forms of energy, including kinetic, gravitational potential, and thermal energy. Understand the principles of energy conservation and how energy is transferred between objects and stores. This quiz will test your knowledge of energy concepts crucial for understanding physics.