Flashcards
P2- crisis cards
Cards in this deck (38)
- 1How is static electricity caused?When insulative materials are rubbed against each other they become electrically charged. Negatively charged electrons are rubbed off one
material and onto the other. - 2How are the material's charges affected by static electricity?The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
- 3How do charged materials act?When two electrically charged objects are brought together they exert a force on each other. Two objects that carry the same type of charge repel.
Two objects that carry different types of charge attract - 4What is electrical current?Electric current is a flow of electric charge.
The size of the electric current is the rate of flow of electric charge. - 5What is potential difference?The potential difference (voltage) between two points in an electric circuit is the energy transferred per coulomb of charge that passes between the points.
- 6How do you find the resistance of a component?The resistance of a component can be found by
measuring the current through, and potential difference across, the component. - 7At constant temp, what is the current of a resistor proportional to?The current through a resistor (at a constant
temperature) is directly proportional to the potential
difference across the resistor - 8How does resistance affect current?The greater the resistance the smaller the
current for a given potential difference across the
component. - 9How does current, PD and resistance affect series circuits?■ the total resistance is the sum of the resistance
of each component
■ there is the same current through each component
■ the total potential difference of the supply is
shared between the components. - 10How does current, PD and resistance affect parallel circuits?the potential difference across each
component is the same
■ the total current through the whole circuit is the
sum of the currents through the separate
components - 11What is significant about currents flowing through diodes?The current through a diode flows in one direction only. The diode has a very high resistance in the reverse
direction. - 12How does an LED emit light?An LED emits light when a current flows through it in
the forward direction. - 13Why are LEDs used more?They require a smaller current so are more efficient and longer lasting.
- 14How does light affect a LDR and why?In the dark and at low light levels, the resistance of an LDR is high, and little current can flow through it.
In bright light, the resistance of an LDR is low, and more current can flow through it. - 15How does temperature affect thermistors?The resistance of a thermistor decreases as the
temperature increases. - 16What is a d.c. and an a.c current?D.c. direct current, one way only (cells, batteries)
A.c. alternating current, changes frequently (mains electricity) - 17Mains electrictyMains electricity is an a.c. supply. In the UK it has
a frequency of 50 cycles per second (50 hertz)
and is about 230 V. - 18What happens if too great a current flows through a component?If an electrical fault causes too great a current, the
circuit is disconnected by a fuse or a circuit breaker
in the live wire. - 19Why do fuse wires' fuses melt?When the current in a fuse wire exceeds the rating
of the fuse it will melt, breaking the circuit. - 20What is an RCCB?Some circuits are protected by Residual Current
Circuit Breakers (RCCBs). They detect a difference in the current between the live and neutral wires. RCCBs work much faster than fuses do. - 21How does earthing work?The earth terminal is connected to the metal casing so that the current goes through the earth wire instead of causing an electric shock. A strong current surges through the earth wire because it has a very low resistance. This breaks the fuse and disconnects the appliance.
- 22How does the resistor change when current passes through it?When an electrical charge flows through a resistor,
the resistor gets hot. - 23What is power?The rate at which energy is transferred by an
appliance is called the power. - 24What is a radioactive substance?Some substances give out radiation from the nuclei
of their atoms all the time, whatever is done to them.
These substances are said to be radioactive. - 25Where does background radiation come from?-Cosmic rays from space
-Certain rocks
-Fallout from nuclear weapons
-Nuclear power accidents - 26Alpha particleHas two neutrons and
two protons, the same as a helium nucleus - 27Beta particle[no idea]
- 28Gamma ray[no idea]
- 29What is a half-life?The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to half.
- 30What elements are used in nuclear fission?There are two fissionable substances in common
use in nuclear reactors: uranium-235 and
plutonium-239. - 31What is nuclear fission?Nuclear fission is the splitting of an atomic nucleus. For fission to occur the uranium-235 or plutonium-239 nucleus must first absorb a neutron which then breaks down the nucleus meaning more neutrons are fired into other nuclei and a chain reaction occurs.
- 32What do nuclei split down into during nuclear fission?The nucleus undergoing fission splits into two smaller nuclei and two or three neutrons and energy is released.
- 33What is nuclear fusion?Nuclear fusion is the joining of two atomic nuclei to form a larger one.
Nuclear fusion is the process by which energy is released in stars. - 34How are stars formed?Stars form when enough dust and gas from space is pulled together by gravitational attraction. Smaller
masses may also form and be attracted by a larger mass to become planets. - 35Why are main sequence stars the most stable?During the ‘main sequence’ period of its life cycle a star is stable because the forces within it are balanced.
- 36Star sequence the same size as sun:1- Protostar forms from dust and gas
Pulled together by gravitational attraction.
2- Forces e.g. gravity in the star are balanced, so it enters main sequence.
3- The main sequence star runs out of hydrogen so fusion slows which causes it to expand to a red giant.
4) Red giant then shrinks to a white dwarf as it collapses under the force of it's own gravity.
5) Eventually cools to form black dwarf. - 37Where do all the elements in the universe come from?Fusion processes in stars produce all of the naturally occurring elements. These elements may be distributed throughout the Universe by the explosion of a massive star (supernova) (due to elements heavier than iron produced) at the end
of its life. - 38Star sequence for stars bigger than sun:1- Protostar forms from dust and gas
Pulled together by gravitational attraction.
2- Forces e.g. gravity in the star are balanced, so it enters main sequence.
3- Runs out of hydrogen for reactions so swells into a red supergiant.
4- Starts to collapse and then massively reverses into a supernova which generates lots of heat, light and elements.
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- Flashcards on P2- crisis cards, created by Jess Clarke on 16/06/2016.
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