Physics 4, 5, 6 Questions Flashcards
What does the live wire do?
It carries the high voltage
Which wire completes the circuit?
The neutral wire
What wire is a safety wire?
The earth wire
What does the earth wire stop from happening?
It stops appliances becoming live
With the polythene rod, where are electrons moved from and to?
Electrons move from the duster to the rod
With the Acetate rod, where are electrons moved from and to?
Electrons are moved from the rod to the duster.
What is Earthing?
When you prevent a dangerous spark from occurring by connecting a charged object to the ground using a conductor. No charge can build up by doing this.
How is paint sprayed to get an even coat when using an electrostatic paint sprayer?
- The spray gun is charged, which charges up the small drops of paint
- Each drop repels each other because they have the same charge
- The object is given the opposite charge, which attracts the paint drops
What frequency can humans hear up to?
20 000 Hz
What is ultrasound used for?
Breaking down accumulation in the body and for body scanning
Why is ultrasound better than X-Ray when looking at a foetus?
It is safer and doesn’t damage living cells. X-Rays are ionising radiation and can cause cancer if exposed to it at a high dose.
When a nucleus emits an alpha particle, what happens to the mass number and atomic number?
The mass number decreases by 4 and the atomic number decreases by 2.
When a nucleus emits a beta particle, what happens to the mass number and the atomic number?
The mass number doesn’t change (because it has lost a neutron but gained an electron) and the atomic number increases by 1 because it has one more proton.
What is half life?
The amount of time taken for half of the radioactive nuclei to decay.
What are the three medical uses of radiation?
- Radiotherapy (for treating cancer cells)
- Tracers in medicine
- Sterilisation of surgical instruments
How do smoke detectors work?
- A weak alpha source is put into the detector.
- The source causes ionisation of the air particles, which allows a current to flow
- When there is a fire, the smoke particles hit the alpha particles instead and reduces the current, making the alarm sound.
What is nuclear fission?
The splitting up of a heavy nucleus which releases heat energy
In terms of nuclear fission, what happens in a nuclear reactor when producing electricity?
A controlled chain reaction takes place in which Uranium or Plutonium atoms split up and release heat energy. This energy is then used to heat water to produce steam. This steam is used to turn a turbine which drives the generator to produce electricity.
What is nuclear fusion?
When two light nuclei combine to create a larger nucleus.
What is cold fusion?
Nuclear fusion that occurs at room temperature rather than at very high temperatures.
Why was cold fusion not accepted?
When other scientists repeated the experiments, they couldn’t produce reliable results, so it was not a realistic method of energy production.
What is a superconductor?
When a metal becomes so cold, it loses all of their resistance. Usually, all metals have some resistance, so when electricity flows through it, it heats up, so some electrical energy is wasted. Without any resistance, no energy is lost as heat, so a superconductor circuit could carry on flowing forever.
With superconducting wires, what can you make?
- Power cables that transmit electricity without losing power
- Strong electromagnets that don’t need a constant power source
- Very fast electronic circuits (because they have no resistance to slow them down)
What are some examples of scalar quantities?
Speed, mass, temperature, distance, time
What are some examples of vector quantities?
Velocity, force, displacement, acceleration, momentum
Where do low polar orbits travel?
Passes very close to the Earth over the poles, so they can scan the whole surface of the Earth.
What are low polar orbits useful for?
- monitoring the weather
- observing the Earth’s surface
- military uses including spying
Where do geostationary satellites travel?
Above the equator, much further away from the Earth
What are geostationary orbits useful for?
- communications - including satellite TV
- global positioning or GPS - which is used for sat navs (satellite navigation systems)
How long does it take for a geostationary satellite to orbit the Earth compared to a low polar?
Geostationary takes 24 hours, whereas low polar takes 2 hours.
With a low polar orbit, their tangential speed is higher. Why is this?
They orbit closer to the Earth, so the gravitational attraction is stronger and also produces a high centripetal force.
What does Newton’s Third Law of Motion say?
Every action has an equal and opposite reaction.
What is meant by Coherent?
Waves with the same frequency and amplitude, and are in phase.
What is constructive interference?
When two waves from the same source arrive in phase and result in a wave with a bigger amplitude.
What is destructive interference?
When two waves from the same source arrive half a wavelength out of phase and cancel each other out.
Do thicker lenses have a longer or shorter focal length?
Shorter
What is a potential divider?
A device that uses two resistors to control the voltage in a circuit
In a Thermistor, at what temperature will the resistance be high?
At low temperatures
In an LDR, at what level of light will the resistance be high?
Dark or low levels of light
In an AND gate, what is the output?
The output is only high if both inputs are high
In an OR gate, what is the output?
The output is always high, except for when both inputs are low
In a NOT gate, what is the output?
The output is opposite the input