XPhysics

Define temperature

Temperature is the average kinetic energy of the particles in a substance.

Define heat

Heat is the total kinetic and potential energy of the particles in a substance.

How do you convert Celsius to Kelvin?

add 273

Describe heat transfer by conduction

Conduction is the transfer of heat through a substance where particles vibrate and bump into neighbouring particles, transferring energy from hot to cold.

Distinguish between conductors and insulators based on their particle structure.

Conductors have closely packed particles that easily transfer energy, while insulators have particles that are further apart, making energy transfer difficult.

Define convection

Convection is the movement of heat that occurs in fluids, such as liquids and gases.

Describe the process of heat transfer by convection.

Heat transfer by convection occurs when particles gain heat energy, causing them to move further apart, which decreases density and allows the warmer, less dense particles to rise. This movement displaces cooler particles, creating a convection current.

Define heat transfer by radiation.

Heat transfer by radiation is the transfer of heat without the involvement of particles, occurring through electromagnetic waves, and can take place in a vacuum.

Explain the difference between emission and reflection in heat transfer.

Emission occurs when a material sends heat away by itself, while reflection happens when heat from another source bounces off the surface of a material.

Describe the characteristics of good and poor radiators of heat.

Good radiators of heat, like black surfaces, absorb and emit heat effectively, while poor radiators, like shiny or white surfaces, reflect most heat and absorb the least.

Discuss how all three types of heat transfer occur in a boiling pot of water.

In a boiling pot of water, radiation from the flame heats the pot, conduction transfers heat through the pot's metal, and convection occurs as heated water rises and displaces cooler water.

Explain how conduction occurs in a metal pot on a flame.

Conduction in a metal pot occurs as the metal particles at the bottom gain heat energy, vibrate faster, and pass this energy to neighbouring particles, allowing heat to move upwards through the pot.

Explain the process of convection currents in water heating.

As hot water at the top cools down, it creates a continuous movement known as convection currents, which spreads heat throughout the water, eventually causing it to boil.

Describe the particle behaviour during the melting process.

In the melting process, tightly packed particles in a solid gain kinetic energy, allowing them to slide over each other and transition into a liquid.

Define latent heat

Latent heat is the amount of thermal energy required to change the state of 1kg of a substance without changing its temperature.

Contrast longitudinal and transverse waves with examples.

Transverse waves include water ripples and light, while longitudinal waves include sound.

Describe the properties of electromagnetic radiation.

Electromagnetic radiation can travel in a vacuum, travels at 3x10^8 m/s, and is transverse.

Recall the relative wavelength and frequency of red and violet light.

Red has a longer wavelength and lower frequency, while violet has a shorter wavelength and higher frequency.

Explain what photons are in the context of electromagnetic radiation.

Photons are packets of energy that electromagnetic radiation carries.

Link the energy of a photon to its frequency qualitatively.

Higher frequency means more energy, as described by E=hf.

Describe everyday uses of radio waves and microwaves.

Radio waves are used for broadcasting, while microwaves are used in cell phones and heating food.

Explain the uses of ultraviolet light.

Ultraviolet light is used for sterilising, curing dental fillings, and phototherapy.

Define frequency, wavelength, amplitude, and period in waves.

Frequency is the number of cycles per second, wavelength is the distance between points in phase, amplitude is the maximum displacement, and period is the time for one oscillation.

Define the prefixes milli, micro, and nano in terms of their numerical values.

Milli is x10^-3, micro is x10^-6, and nano is x10^-9.

Recall the law of reflection and its application.

The angle of incidence equals the angle of reflection.

Describe how the law of reflection is used in satellite communication.

Satellites use the law of reflection to direct signals back to Earth.

Explain refraction and its relation to Snell's law.

Refraction is the bending of a wave as it passes into a medium of different optical density, described by Snell's law.

Explain Snell's law and its formula.

Snell's law describes the relationship between the angles of incidence and refraction when light passes between two different media. The formula is n₁sinθ₁ = n₂sinθ₂, where n is the refractive index.

Define refractive index and its significance.

The refractive index (n) is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in a medium (v). It is a dimensionless quantity that indicates how much light bends when entering a medium.

Define diffraction

Diffraction is the bending of waves as they pass through a gap or around a barrier.

Explain how wavelength affects diffraction.

Longer wavelengths result in greater diffraction, while shorter wavelengths lead to less diffraction.

Describe the relationship between gap size and diffraction.

Smaller gaps lead to more diffraction, while larger gaps cause less spreading and create sharper shadows. A gap similar in size to the wavelength causes the most diffraction.

Explain why we hear bass sounds more easily than high-pitched sounds in terms of diffraction.

Bass sounds have longer wavelengths, allowing them to diffract around obstacles more effectively than high-pitched sounds, which have shorter wavelengths and diffract less.

Describe how light behaves when passing through small gaps.

Light has a shorter wavelength compared to sound, which means it does not bend around corners as easily. This is why we can hear sounds from around corners but cannot see light.

Define total internal reflection (TIR) and its conditions.

Total internal reflection occurs when light travels from a denser medium to a less dense medium, and the angle of incidence exceeds the critical angle. In TIR, all light is reflected back into the denser medium.

Explain how to calculate the critical angle for total internal reflection.

The critical angle (θc) can be calculated using the formula sinθc = n2/n1, where n1 is the refractive index of the denser medium and n2 is that of the less dense medium.

Describe some applications of total internal reflection.

Total internal reflection is used in devices like telescopes and periscopes, as well as in diamonds to enhance their sparkle. However, it is dependent on specific refractive indexes.

Define an echo

An echo is a sound wave that reflects off a surface.

Define magnetic field.

An area where a ferromagnetic metal or charge experiences a force.

State the units for magnetic field strength.

Tesla (T).

Describe the right hand rule for determining the direction of magnetic field lines around a solenoid.

Fingers curl in the direction of the current, and the thumb points to the north pole.

Describe the uses of electromagnets in everyday life.

Electromagnets are used in magnetic locks, headphones, and radiation therapy to guide charged particles.

Explain how AC is produced in a generator.

AC is produced by motion in a magnetic field.

Describe the function of step-up and step-down transformers.

Transformers are used to adjust voltage levels for power lines and appliances.

Calculate energy efficiency given primary and secondary power.

Energy efficiency is calculated as (P secondary / P primary) * 100%.

Compare nuclear fission and fusion in terms of what it involves and waste produced.

Fission involves splitting a large nucleus and produces radioactive waste, while fusion involves joining small nuclei and produces little or no long-lasting radioactive waste.

Does nuclear fission or fusion produce more energy?

Fusion

Where are nuclear fission and fusion used, and where is it easiest to do them?

Fission is used in nuclear stations and atomic bombs, and are easy to do on Earth. Fusion powers the Sun and stars, and is hard to do on Earth.

Describe how hydroelectric power is produced.

Hydroelectric power uses the kinetic energy of moving water to turn turbines, which drive generators to produce electricity.

Explain how wind turbines generate electricity.

Wind turbines convert the kinetic energy of wind into electrical energy by using blades to capture wind force, turning a rotor connected to a generator.

Describe the process of geothermal electricity production.

Geothermal energy is produced by accessing steam from heated groundwater in geothermal reservoirs to turn turbines.

Discuss the advantages and disadvantages of hydroelectric power.

Advantages: Renewable and cost-effective. Disadvantages: Limited suitable locations and droughts can reduce production.

Discuss the advantages and disadvantages of wind energy.

Advantages: No emissions and space efficient. Disadvantages: Noise pollution and wind availability can be inconsistent.

Discuss the advantages and disadvantages of geothermal energy.

Advantages: Renewable and reliable with a small land footprint. Disadvantages: Location specific and can be expensive.

Describe how solar panels work.

Solar panels convert sunlight into electricity using the photovoltaic effect. The photons in sunlight give energy to electrons in the solar cells. The energy knocks electrons loose and creates an electric current.

Discuss the advantages of solar power.

Advantages of solar power include being renewable, having no emissions, low maintenance costs, reducing electricity bills, creating jobs, and decreasing reliance on fossil fuels.

Identify the disadvantages of solar power.

Disadvantages of solar power include dependence on time of day and weather, high initial costs, expensive storage, space requirements, lower efficiency in certain locations, and aesthetic concerns.

Define and explain specific heat capacity.

Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance by 1 degree Celsius.

Contrast longitudinal vs transverse waves.

Longitudinal waves have particle motion parallel to wave direction (e.g., sound), while transverse waves have particle motion perpendicular to wave direction (e.g., light).

What is the order of the electromagnetic spectrum?

Radio waves, micro waves, infrared, visible light, UV, X-rays, gamma ray

Recall relative wavelength/frequency of the electromagnetic spectrum.

Gamma rays have the shortest wavelength and highest frequency, while radio waves have the longest wavelength and lowest frequency.

Explain why electricity is transmitted at high voltage/low current.

Electricity is transmitted at high voltage and low current to minimize energy loss due to resistance in the transmission lines. Higher voltage allows for lower current, which reduces heat loss and improves efficiency.