# physics p4

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how can an insulating material become electrically charged?
by rubbing it against another insulating material. Electrons (negative charge) transfer from one material to the other leaving one positively charged and the other negatively
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how can a charged object be discharged?
by earthing it, when an object discharges electrons are transferred from the charged object to earth.
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what will two insulating materials with the same charge do?
repel each other, however two materials with different charges will attract each other.
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how does spray painting work?
the paint particles are given a negative charge so that they repel each other, forming a fine spray. This ensures the paint is applied evenly. the panel that is sprayed is positively charged so it attracts the negatively charged paint.
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how do defibrillators work?
two paddles are charged and put in good electrical contact with the patient's chest the charge is then passed through the patient to make the heart contract.
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what is a circuit?
a complete loop that allows an electrical current to flow. electrons flow around the circuit from the negative electrode of the power source.
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what is resistance?
a measure of how hard it is to get a current through a component in a circuit at a particular voltage (potential difference). measures in ohms.
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how can current through a circuit be controlled?
by varying the resistance. there are two types of resistor: a fixed resistor has a constant resistance, the bigger the resistance the smaller the current that flows. And a variable resistor (or rheostat) has a changeable resistance
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how do you calculate resistance?
resistance= Voltage / Current
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what are the three wires in a plug?
live wire: (brown) carries current to the appliance at a high voltage. Neutral wire : (blue) completes the circuit and carries current away from the appliance. Earth wire: (green and yellow) safety wire that stops the appliance becoming live.
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What are fuses and circuit breakers?
safety devices, designed to break a circuit if a fault occurs. this prevents fires, injuries and deaths
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how do you calculate Power?
power (W)= Current (A) X Voltage (V)
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What is Ultrasound?
Ultrasound is sound waves with frequencies above the upper limit of the human hearing range. Ultrasound travels in a longitudinal wave.
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What can Ultrasound waves be used for?
used in medicine and scanning the body. can also break down kidney stones so they can be removed from the body naturally.
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what do radioactive materials give of?
Nuclear radiation from the nucleus of each of their atoms. the atoms are unstable and decay naturally.
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By the number of nuclear decays emitted per second
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What happens during Alpha emission?
The atoms decays by ejecting an alpha particle (helium nucleus made of 2 protons ans 2 neutrons) from the nucleus.
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what happens during Beta emission?
the atom decays by changing a neutron into a proton and an electron. the high-energy electron ejected from the nucleus is a beta particle
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what is Half-Life?
the time it takes for half the undecayed nuclei in a radioactive substance to decay. if the substance has a very long half-life then it remains active for a very long time.
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What are Igneous rocks?
can contain uranium atoms which decay to produce stable atoms of lead.
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how can you date rocks?
measuring the proportion of uranium and lead in the rock. Knowing the half-life of uranium.
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occurs naturally in our environment and is all around us. releasedby - radioactive substances in soil and rocks, cosmic rays from outer space.
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used a tracers in industry and hospitals. used to track dispersal of waste, find leaks and blockages in underground pipes, find routes of underground pipes.
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what do smoke detectors contain?
Ameriucium-241 : an Alpha emitter. Emitted particles cause air particles to ionise, and the ions formed are attracted to the oppositely charged electrodes.
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how do smoke detectors work?
the alpha particles are absorbed by the smoke particles, less ionisation takes place, a smaller current than normal flows and then the alarm sounds.
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what are electromagnetic waves?
X-rays and Gamma Rays with similar wavelengths but are produced in different ways.
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how are gamma rays used to treat cancer?
a wide beam of gamma rays from a source outside the body is focused on the tumor, the beam is rotated around the outside of the body with eh tumor at the centre, this concentrates the gamma rays on the tumor but minimizes damage to the rest of the bo
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What are tracers?
small amounts of radioactive materials ( a short half-life) which are swallowed or injected into the patient.
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what do power stations burn?
fossil fuels. this produces heat which boils water and creates steam.
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What is fission?
Nuclear fission is the process by which heat energy is released when a radioactive nucleus splits. this heat energy can be used in a nuclear reactor.
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what is fusion?
heat energy is released when nuclei join (fuse) together. happens in stars.
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## Other cards in this set

### Card 2

#### Front

how can a charged object be discharged?

#### Back

by earthing it, when an object discharges electrons are transferred from the charged object to earth.

### Card 3

#### Front

what will two insulating materials with the same charge do?

### Card 4

#### Front

how does spray painting work?

### Card 5

#### Front

how do defibrillators work?

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