Paper 2 - 2 Flashcards
(22 cards)
Define static charge
An electric charge that stays on the surface of an insulator. It does not flow unless given a path.
How is a static charge created between two insulators?
When two insulators rub together, friction causes electrons to transfer to one object. One becomes positively charged and the other negatively charged.
How does an earth wire work?
A conducting material connecting the charged object to earth. Electrons flow through it, equalising the charge.
Why don’t insulators need earth wires?
The insulating object has a charge but charge cannot move through it. It stays there unless large enough to jump to another object, causing a spark.
What happens when a conductor has a static charge?
The charge spreads across the material. If a path is available, it discharges suddenly, which can cause a spark or shock.
In static electricity terms, how does a photocopier work?
Static charge is used to create a pattern of charge. Ink is oppositely charged and attracted. Heat is applied to fix the image.
Explain how a transformer is useful in large-scale transmission of energy.
A step-up transformer is used before transmission to increase voltage and decrease current. Lower current means less heating in cables and less energy lost in transmission. A step-down transformer is used after to reduce voltage for safety.
What are the 3 magnetic materials?
Iron, cobalt, and nickel.
What metal is used in electromagnets?
Soft iron.
Fingers for Fleming’s left hand rule?
Thumb is motion, first finger is field, second finger is current.
Give an example of a soft magnetic material.
Iron.
Give an example of a hard magnetic material.
Steel.
Describe how neutrons released in nuclear fission cause a chain reaction.
Neutrons are absorbed by another radioactive nucleus, causing the nucleus to split and release more neutrons. This process repeats (e.g. uranium-235).
Describe the motion of particles in a liquid.
Random motion; particles slide over each other.
Give reasons why fusion does not occur at low temperatures and pressures.
Nuclei are positively charged and repel each other. High temperature gives nuclei enough kinetic energy to collide, and high pressure pushes them together.
Why does a changing magnetic field induce a voltage?
A change in magnetic field causes a change in flux through a coil, which induces a voltage in the coil.
State why transformers don’t work on direct current.
DC gives a constant magnetic field. Transformers require a changing magnetic field to induce a voltage in the second coil.
How do observations of redshift support the big bang theory?
Redshift is proportional to speed, and speed is proportional to distance. More redshift means galaxies are moving away faster, showing the universe is expanding.
Why is a high specific heat capacity useful?
It allows a material to store a lot of thermal energy with small temperature change, absorbs heat slowly, and releases heat slowly, helping maintain stable temperature.
State the principle of moments.
When an object is balanced, total clockwise moment equals total anticlockwise moment.
State what is meant by specific heat capacity.
The amount of energy required to raise the temperature of 1 kg of a substance by 1°C.
What is Newton’s third law of motion?
When one object exerts a force on another, it experiences an equal force in the opposite direction.
