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40 Cards in this Set
- Front
- Back
Electroscope
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*an instrument used to detect charged objects.
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calculate electric force
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F= qE
force= charge x electric field |
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force to distance
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*the strength of a field decreases the farther you get from the source.
Inverse square law-because the intesity diminishes as the square the distance increases. |
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Like charges?
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repel
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Unlike charges?
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attract
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Define charging by induction
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*A moving magnet induces electric current to flow in a circuit.
*Fardays Law of induction- voltage is proportional to the rate of change in the magnetic field through the coil. |
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Define Polarization
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*seperation of the positive and the negative change in an objects atoms due to the effect of an elctric field.
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Where are magnetic fields the strongest?
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If the field lines are close they are stronger.
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What direction do magnetic field lines point?
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*magnetic field lines always point away from the north pole and toward the south pole
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How or why does an electric motor spin?
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*as the rotor spins, the cummutator reverses direction of the current in the electromagnet.
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Define generator
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*converts kinetic energy into electrical energy using the law of induction.
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Define wavelength
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*the length of one complete cycle of a wave.
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Define hertz
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*unit of 1 cycle per second. Frequency measured in hertz.
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Define period
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*the time it takes to repeat 1 cycle.
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Define absorption
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*the decrease in amplitude of a wave as it passes through material and loses energy.
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Define longitudinal waves
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* a wave that has oscillations in the same direction as the wave travels.
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Define transverse wave
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*a wave with oscillation that are perpendicular to the direction the wave travels.
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Define closed circuit
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*circuit with a complete path for the current to flow.
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What is color?
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*the perception of energy of light.
*red-lowest energy *violet-highest energy |
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Define fuse
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*each parallel circuit has a "fuse" or a circuit breaker to stop the current if it exceeds the safe amount.
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Define watt
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*unit of power
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Define circular waves
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*wave crests form a pattern of circular wave fronts.
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Define plane waves
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*wave crests form a pattern of stright line wave fronts.
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Inverse square law rule in regards to light waves.
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*describes a quantity that varies inversely with the square of the distance.
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Define transformers
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*A device that uses induction to convert AC electrical current and voltage to another AC current and voltage while keeping the power about the same.
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Define interference
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*a pattern of pressure, brightness, amplitude or other wave characteristic that comes from adding more than one wave of the same kind.
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Define refraction
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*the bending of a wave as it travels across a boundry.
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Define reflection
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*the wave bouncing off a surface.
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Define frequency
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*the number of cycles per second, measured in hertz (Hz)
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Radio Waves
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*radio waves-lowest frequency of electromagnetic waves with a wavelength greater than tens of centimeters.
*example: 101.1 radio station means that the broadcast is = to 101 megahertz. |
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How does changes in force relate to distance?
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*the force from a magnet decrease faster than an inverse square law. This is because all magnets have two opposite pole, not one.
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What does an increase in the number of wires in a magnetic field do?
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*a single wire can be looped into a coil, concentrating the magnetic field at the coil's center.
*when a wire is in a circular loop, field lines on the inside of the loop squeeze together. *the most common form of electromagnetic device is a coil with many turns called, "solenoid" |
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Standing Wave
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*a wave that is confined in a space.
*standing waves include sound, water, and light. |
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Sound Wave
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*anything that vibrates creates sound waves, as long as there is contact with other atoms.
*not all sounds can be heard. *humans can hear between 20 Hz and 100,000 Hz. *sound is a traveling oscillation of atoms. |
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List primary colors from the lowest to the highest energy
*see page 486 |
red-460
orange-490 yellow-520 green-570 blue-640 violet-750 |
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Series Circuit
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*contains only one path for electric current to flow.
*current is the same at all points in the circuit. |
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Parallel Circuits
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*a circuit with more than one path for the current.
*each path in the circuit is called a branch. *all of the current entering a branch point must exit again. The rule is known as Kirchhoff's Current Law |
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Short Circuit
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*a parallel path in a circuit with very low resistance.
*example diagram on page 326. |
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Electric companies
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*they do not change by the volt, amp or ohm. They charge by the unit=watt.
*electric companies charge by how many Kilowatts hours are used during a period of time. *one kilowatt means that power has been used for one hour. |
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Calculate current in volts
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P=IV
power/watts= current X Voltage |