GENERA; Flashcards
Hairdryer takes current of 5.5A Why should you use a 7A fuse (1)
Nearest above
Hairdryer has a plastic case so there is no need for an earth wire connection in the plug. Explain why the hairdryer is still safe to use (2)
- Plastic insulator / doesn’t conduct
- No risk of shock / electrocution
Describe how the student should use each instrument to make her measurements as accurate as possible. (4)
Measuring cylinder; Electronic balance
MC - flat surface, eyes to water level
EB - Set to zero, avoid disturbing balance
For a density experiment, state one factor that she should keep the same throughout her experiment and why (2)
- Temperature
- Can affect density/volume
What is refraction (1)
- Change in direction of waves at a boundary
- draw around block
- mark positions of incident and emergent rays
- (remove block and) draw refracted ray
- measure i; measure r
- range of values;
- (graph of) sin i against sin r
- graph is straight line
- gradient gives refractive index
Why would a pattern show a uniform magnetic field (1)
- Parallel field
Explain how to produce a uniform magnetic field (3)
- two (permanent / bar) magnets
- pole pieces north facing South
- magnets the correct distance apart
Describe the method the teacher should use to correct for background radiation. (3)
- Remove source
- measure background
- find mean
- subtract (background value) from experimental values (with source);
Technetium-99 is a gamma emitter with a half-life of 6 hours. Radioactive tracer in medicine.
Technetium-99 is injected into a patient’s bloodstream and carried around the body by the blood.
The radiation it emits is detected outside the body. Explain why technetium-99 is suitable for use as a tracer in this way.
(3)
- (gamma) can be detected outside the body
- long enough half life to get around the body (for use as tracer)
- half life falls to low levels soon after use;
Describe how a sound wave moves through the air. (3)
- oscillation of (air) molecules
- longitudinal
- directions of vibration and propagation are parallel
- compression / rarefaction /pressure wave;
Which force is responsible for artificial satellites following their paths around the Earth? (1)
- Gravity
Moons are natural satillites of…(1)
- Planets
State one similarity in the movement of planets and comets.
State one difference between the movement of planets and comets. (2)
- Both orbit the sun
- Different shape orbit
Explain how the speed of a comet changes as it moves. (2)
- Speeds up closer to sun
- gravitation attraction from the Sun is stronger when the comet is close
Suggest two safety precautions you should take when putting a plug into a mains socket (2)
- beware of frayed cable
- beware of damaged plug
- beware of water
Describe the difference between a.c. and d.c. (2)
d. c. – electrons/current motion only in one direction
a. c. – electron/current motion reverses (regularly)
Describe how the earth wire can act together with a fuse as a safety device. (2)
- large current in earth wire / charge flows to earth
- large current in fuse ; fuse melts
- stopping electrocution
Explain why a mains plug can be safe to use even though it has no earth connection. (2)
- double insulation of plug, cable or appliance
- insulation stops current / does not conduct
- electric shocks are currents idea of a second insulation layer in case the first fails
Describe how the students should find the average mass of a winged seed (2)
- Measure using balance
- Repeated readings
Describe how radioactivity can be used to estimate the age of archaeological discoveries such as wooden boats and animal bones. (4)
- (living things contain) carbon (14)
- C14 is a beta emitter
- (radio)activity decreases (over time)
- (estimate) half-lives (since material was alive)
- ratio of C14 to C12 is fixed in living material
Compare the processes of transferring energy by conduction and transferring energy by convection (3)
- CONDUCTION: from particle to particle
- by collision
- CONVECTION: particles able to move
- transfer the energy by kinetic energy
Useful light energy emitted in J/s : 5
Describe what happens to the energy wasted by the filament lamp. (2)
- transformed into thermal energy
- dissipated to surroundings
State two benefits of connecting lamps in parallel. (2)
- independent control
- failure of one allows others to continue working
State two conditions required for total internal reflection to happen. (2)
- Must be more (optically) dense to less (optically) dense change;
- Angle of incidence > critical angle;
The image in a plane mirror is a virtual image.
How can you tell this from your diagram? (1)
- Rays do not actually meet at the image
Suggest 3 advantages of sending signals using optical fibres. (3)
- Less prone to noise
- less prone to heating
- send more information (per second)
- more data (per second)
Describe the method the student should use to investigates how the resistance of a wire depends on its length (5)
- connect (crocodile) clip to wire
- Read ammeter and read voltmeter
- For known length
- measure length with a ruler
- Repeat readings in different places along the wire
- Take readings for different lengths
- Check meters for zero errors
- Disconnect/switch off between readings
- To avoid heating the wire;
How to make a measuring cylinder give the most precise measurement? (1)
- Smallest scale divisions
The most precise measuring cylinder may not give an accurate reading. Suggest why. (1)
- incorrect scale / calibration
- misreading scale / parallax /not at eye level
- meniscus makes it difficult to read
- might not be level / flat; reading may be between divisions;
Explain how nuclear fission can lead to a chain reaction. (3)
- Nucleus splits
- Releasing neutrons
- Which are absorbed by different (uranium) nuclei;
Nuclear fission releases energy. Explain the form that this energy takes. (2)
Kinetic (energy of particles)
- Of (fission) products / (daughter) nuclei / neutrons
In a nuclear power station, what is the purpose of a moderator (1)
- Slow down neutrons
Suggest 2 properties of radio waves that makes them suitable for use in communication. (2)
- Travel quickly / at the speed of light
- Can code information
Can travel long distances / through buildings / walls / objects
Not harmful/dangerous; can diffract / reflect;