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100 Cards in this Set
- Front
- Back
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An Atom consists of...
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a small positively charged nucleus surrounded by negatively charged electrons
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All electrostatic effects are due to...
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the movement of electrons
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When a polythene rod is rubbed with a duster...
When an acetate rod is rubbed with a duster... |
The rod becomes negatively charged
The rod becomes positively charged |
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Electric shocks can be avoided by...
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connecting an earth wire to items that could become charged, standing on an insulating mat, wearing shoes with insulated soles, or using anti-static sprays/liquids/cloths
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A dust precipitator works by:
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There is a grid that is charged at the bottom of the chimney, and on both sides of the chimney two plates with the opposite charge to the grid. As dust passes the grid it takes on that charge, and is then attracted to the plates. At regular intervals the plates vibrate and the dust drops onto a collector.
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Paint spraying using electricity works by:
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The spray gun is charged, and the bike given the opposite charge. As the paint passes the nozzle, it is given the same charge as the gun, and the particles repel each other and spread out for an even spray. The particles are then attracted to the bike so they stick to it.
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power=
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voltage x current
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resistance=
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voltage/current
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A... changes the resistance
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variable resistor/rheostat
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If the resistance is fixed, as voltage increases...
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current increases
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If the power supply is fixed, as resistance increases...
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current decreases
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The live wire...
The neutral wire... The earth wire... |
carries the voltage round the house
completes the circuit, providing a return path is connected to ground the appliance in case of the item becoming live |
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Resistance is measured in...
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Ohms
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Ultrasound is at...
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20,000Hz
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In a longitudinal wave:
Regions of higher pressure: Regions of lower pressure: |
Compressions
Rarefactions |
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In a longitudinal wave the vibrations of the particles are...
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parallel to the wave
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In a transverse wave, the vibrations of the particles are...
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at right angles to the wave
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When an ultrasound is used to break down kidney stones...
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The beam is directed at the stone, the stones break down into smaller pieces, and are then excreted
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Ultrasound is used instead of x-ray because
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it can produce images of soft tissues and doesn't damage living cells
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Ultrasound can be used for full body scans because
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when it is reflected from surfaces in the body, the time that it takes to travel back is recorded, and by the time it takes it to get back and the amount of the wave absorbed a picture can be built up of the type of tissues and their depth
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Nuclear radiation causes... by...
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ionisation, removing or gaining electrons from atoms
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The half-life of a radioisotope is...
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The time it takes for half of it to decay
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The three types of radiation are...
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Alpha, beta, gamma
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Nuclear equation for alpha decay...
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238 234 4
U -> Th + He 92 90 2 |
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Nuclear equation for beta decay...
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14 14 0
C -> N + e 6 7 -1 |
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When gamma is given out, how does the element decay?
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It doesn't. Gamma is an energy wave.
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Background radiation comes from...
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Rocks
Space Radioactive waste Hospitals |
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Radiation is used in...
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Smoke alarms
Medical/Leak tracers Dating rocks Carbon Dating |
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Cobalt-60 is used to...
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treat cancer
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X-rays are made by firing...
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high speed electrons at tungsten targets
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Radiation is used medically to...
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Kill tumours, as tracers
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In a nuclear power station...
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uranisum-235 is bombarded with neutrons until it splits, reducing more neutrons that could strike the nucleus of other atoms, causing a chain reaction. This releases a large amount of energy. Boron control rods are used to absorb excess neutrons if the reaction gets too violent. A graphite moderator also is used to slow down the neutrons.
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Nuclear fusion is...
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two light nuclei fusing together releasing heat energy.
Safely replicating fusion on earth has not yet been possible. |
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Gravity is...
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the force of attraction between every object
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Any object moving in a circle needs a ... this is called...
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force towards the centre of the circle, centripetal force
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Gravitational forces obey an
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inverse square law
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time=
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distance/speed= (2pir)xspeed
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A polar satellite orbits...
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100-20km above earth
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A geostationary satellite orbits
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above the equator
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A scalar quantity has..., while vectors have... and...
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magnitude, magnitude and direction
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s
u v a t |
Distance
Initial velocity Final velocity Acceleration Time |
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Gravity causes an acceleration of...
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10metres per second per second
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When a ball is thrown... speed is constant
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horizontal
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Newton's third law is...
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Every action has an equal and opposite reaction
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Momentum=
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mass x velocity
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force=
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change of rate of momentum
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Microwave signals are sent into space from a
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parabolic transmitter
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The ionosphere reflects frequencies below...
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30Mhz
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Geostationary sattelites orbit...
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36,000 kilometres above the equator
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The smaller the gap, the...
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greater the diffraction
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Television aerials must have... with the transmitter
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line of sight
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Interference is caused by...
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a crest and trough from two waves hitting each other and cancelling each other out
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Constructive interference...
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The waves meet in phase
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Destructive interference...
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The waves meet out of phase
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Unpolarised light=
Polarised light= |
Many planes of oscillation
One plane of oscillation |
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refractive index=
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Speed of light in vacuum/speed if light in medium
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Optical fibres rely on...
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total internal reflection
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The critical angle is the...
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angle of incidence in the more dense medium that produces an angle of refraction of 90 degrees in the less dense medium.
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A parallel beam of light from a distant object can be converged to a focus in the...
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focal plane
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magnification=
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image size/object size
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An image made by a magnifying glass is a... and cannot be... because...
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virtual image, projected onto a screen, no light passes through it
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resistance=
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voltage x current
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The higher the resistance, the
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lower the current
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A variable resistor works by...
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Changing the length of wire in a circuit, the more wire, the more resistance
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When electrons collide with the atoms in a filament bulb,
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The atoms vibrate more, leading to increased collision, temperature and resistance
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V out =
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R
2 -------------- V R + R 2 1 2 |
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The resistance of a thermistor increases with...
The resistance of a LDR increases with... |
lack of temperature
less light |
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In a transistor, a small base current can...
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switch on a greater current through the collector
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Two transistors combined can make an....
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AND gate
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An AND gate requires...
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Both inputs on.
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A NAND gate requires...
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Neither inputs on
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An OR gate requires...
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Either input on.
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A NOT gate requires...
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No input
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A NOR gate requires...
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Both inputs off.
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A relay works...
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like a switch, but switches between normally open contacts (NO) and normally closed contacts (NC)
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The direction of a field around a wire can be found using...
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the right hand grip rule
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When a wire is placed between two magnets, it moves out of the gap when...
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the current is turned on
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To predict the direction a motor turns, you use...
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Flemings left hand rule
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To make a motor turn faster,
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the number of turns on the coil is increased, the size of the current is increased or the strength of the magnetic field is increased
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The direction of the current in a motor is reversed... This is to make sure...
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every half turn, the force is always in the same direction
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The job of the commutator is...
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to make the motor continue to spin
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A... increases the force on the coil and keeps it constant as the motor turns
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radial field
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When a wire is moved between... a ...is induced and...
If the wire is moved downwards, the... is reversed and the... is in the opposite direction. |
two poles of a magnet, voltage, current passes
voltage current |
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The voltage generated in a wire depends on...
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the speed it moves in between the poles of a magnet
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Increasing the speed of rotation of the electromagnet in a power plant increases...
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the current induced and the frequency of the voltage
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Increasing the number of turns in the electromagnet on a generator...
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increases the magnetic field and the voltage
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Slip rings are connected to the ends of the coil to allow...
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the coil to spin without winding the wire around itself
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Brushes are...
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contacts that touch the slip rings and complete the circuit
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A transformer consists of...
The input AC is connected to... and the output AC is obtained from... |
two coils of wire wrapped round an iron core
primary coil secondary coil |
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Step down transformers have...
Step up transformers have... |
more turns on the primary coil
more turns on the secondary coil |
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voltage across the primary
------------------------------------------- = voltage across the secondary |
number of turns on the primary coil
-------------------------------------------------------- number of turns on the secondary coil |
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power loss=
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2
current x resistance |
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Diodes need an input of around...
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0.6V before they start to work
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A diode consists of...
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a piece of n-type and p-type semiconductor joined together
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N-type semiconductor has...
P-type semiconductor has... The junction between the two has... |
an excess of electrons
a lack of electrons ( the gaps where they should be are called holes) None of either |
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A diode only allows...
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current to pass one way
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If the positive terminal is connected to the n-type...
If the positive terminal is connected to the p-type... |
The junction widens and no current passes
The junction narrows until it disappears and current passes |
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A bridge circuit consists of...
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four diodes
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A capacitor stores...
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electrical energy
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To make the output of a bridge circuit smoother...
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a capacitator can be added
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