OCR Additional Science B P4

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  • Created on: 20-04-14 14:37
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Physics 4
Generating static electricity
An insulating material can become charged when it's rubbed with another insulating material. Dusting
brushes can be charged so they attract dust when they pass over the brush. Synthetic clothing can become
charged due to friction between the clothing and the person's body. When the clothing is removed from the
body, static sparks are sometimes produced
Discharging static electricity
A charged object can be discharged by earthing it. The electrons are transferred from the charged object to
earth. If you become charged then earthed, you could get an electrostatic shock
Problems of static electricity
Dirt and dust can be attracted to insulating materials (TV and computer screens)
Flour mills and petrochemical factories have atmospheres with flammable gases or high concentrations
of oxygen. A discharge of electricity (spark) can lead to an explosion
Situations where large amounts of electricity could flow through your body to earth
Repulsion and attraction
Two insulating materials with the same charge repel
Two insulating materials with opposite charges attract
Spray painting
Smoke
precipitators
This removes smoke
particles from
chimneys. Metal grids
are connected to a high voltage. The dust particles lose electrons and
become positively charged as it passes the grid. They are attracted to
the negative charged plates, where they form large particles that fall
back down the chimney when they are heavy enough.
Defibrillators
Two paddles are charged and put in good
electrical contact with the patient's chest
using gel. Charge is then passed through
the patient to make the heart contract.
Circuits
Circuit ­ a complete loop that allows an electrical current to flow. Electrons flow from negative to positive

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Fixed and variable resistors
Resistance ­ measure of how hard it is to get a current through a component in a circuit at a particular
voltage
A fixed resistor has constant resistant.…read more

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Wavelength ­ distance between two points on two disturbances
Frequency ­ number of waves produced in 1 second
Amplitude ­ maximum disturbance by a wave
Applications of ultrasound
Scanning the body with ultrasound can produce a picture of the body's organ. They can cause kidney stones
to vibrate. The stones break up and then can be passed out of the body in urine.…read more

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This occurs naturally in our environment and is all around us. Most background radiation is released by:
radioactive substances in soil and rocks and cosmic rays from outer space. Some radiation comes from
man-made sources and waste products. Industry and hospitals contribute to radiation levels.
Tracers
Radioisotopes are used as tracers in industry and hospitals.…read more

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It happens easily in star, but isn't practical on the earth yet.
Small scale fission
1. Uranium atom is hit with a neutron
2. Nucleus splits into two smaller nuclei
3. Energy and new neutrons are released
4. The new atoms formed are radioactive
Large scale fission
They stop nuclear reactions getting out of control by placing control rods in the reactor. They absorb
some of the neutrons, preventing further fissions.…read more

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