The discovery of electromagnetic induction is credited to
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Joseph Henry in America.
Michael Faraday in England
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Electromagnetic induction is employed in
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mobile phones.
hybrid automobiles.
electric power lines.
triggering traffic lights
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When a change occurs in the magnetic field in a closed loop of wire
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a voltage is induced in the wire.
electromagnetic induction occurs.
a current is created in the loop of wire
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If you thrust a magnet into a closed loop of wire, the loop will
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have a current
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Thrust a magnet into the opening of a rubber band and it
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do nothing
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When voltage is induced in a coil of wire, current is
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also induced
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Electromagnetic induction occurs in a coil when there is a change in
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magnetic field intensity in the coil
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When a bar magnet is thrust into a coil of copper wire, the coil tends to
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repel the magnet as it enters
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Voltage can be induced in a wire by
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changing the current in a nearby wire.
moving the wire near a magnet.
moving a magnet near the wire.
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Magnetic field strength inside a current-carrying coil will be greater if the coil encloses a
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rod of iron
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Faraday's law underlies the operation of
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a shake flashlight.
an electric guitar.
the changing of traffic lights
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When a magnet is moved to and fro in a wire coil, voltage is induced. If the coil has twice as many loops, the voltage induced is
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twice
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The metal detectors that people walk through at airports operate via
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Faraday's law
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Disregarding the effects of friction, a cyclist will coast farther when a lamp powered by a wheel generator is
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turned off.
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If you drop a bar magnet in a vertical copper pipe it will fall slowly because
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it induces a magnetic field in the pipe that resists motion of the magnet
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A device that transforms electrical energy to mechanical energy is a
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motor
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A device that transforms mechanical energy into electrical energy is a
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generator
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The current produced by a common generator is
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ac
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A turbogenerator produces
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not power and not energy, but transforms energy from one form to another/ transforms them does not creat them
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An electric motor is very similar to
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an electric generator
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A generator armature is more difficult to rotate when supplying electric current due to
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an induced magnetic field in the windings that resists change
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The rate at which energy is transferred is
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power
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A transformer actually transforms
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voltage
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A transformer transforms voltage while
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transferring energy from one coil to another
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The output power of an ideal transformer is
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equal to the input power
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Compared to the primary voltage, the secondary voltage can be
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the same, lower or higher any of these
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The principle difference between a step-up and step-down transformer is
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different ratios of turns of wire for each.
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An efficient step-up transformer boosts
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voltage
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An efficient step-down transformer decreases
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not power and not energy neither of these
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The primary of a transformer is the coil connected to
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the input power line
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The secondary of a transformer is the coil connected to
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the load
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An iron core in a transformer
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guides magnetic field lines
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A step-up transformer steps up voltage by ten times. If voltage input is 120 volts, voltage output is
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1200 10 x 120=1200
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A step-up transformer steps up voltage by ten times. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is
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coils get same power 100w
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A certain transformer doubles input voltage. If the primary coil draws 10 A of current, then the current in the secondary coil is
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5 A if the transformer doubles than the secondary coil is half of the 1st coil
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Neon signs require about 12,000 volts to operate. If the circuit uses a 120-volt power source, the ratio of primary to secondary turns on the transformer should be
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1 primary to 100 secondary
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If the primary of a transformer is connected to a dc power source, the transformer would have a voltage output
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only while being connected or disconnected
dc stands for connected and disconnected
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Disconnect a small-voltage battery from a coil of many loops of wire and a large voltage may be produced by
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the sudden collapse in the magnetic field
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Underlying the concept of self-induction is
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Faraday's law
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The principal advantage of ac power over dc power is that
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ac voltage can be transformed via conventional transformers
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Between the consumer and the power plant, most importantly, are
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step down transformers
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Power is transmitted at high voltages because the corresponding current in the wires is
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low so that overheating of the wires is minimized
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The high voltage that is important in a power line is high voltage
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between the parallel wires of a line
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High-voltage wires in power lines are not high-current wires because the current in them is
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not the same as the current that powers the distant load.
proportional to the voltage drop from beginning to end of each line, rather low
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When voltage is stepped up in a transformer, current is stepped down. But Ohm's law tells us that greater voltage means greater current, not less current. How then can current be lower when voltage is increased?
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Ohm's law applies to the circuit connected to the secondary, not to the transformer.
Current in the secondary is lower when compared to the greater current drawn by the primary
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Rapid change of a magnetic field induces
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an electric field
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In the field induction credited to Maxwell, wires
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wires are not needed
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The induced electric and magnetic fields of Maxwell are
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perpendicular to each other
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Induced electric and magnetic fields result in
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electromagnetic waves
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A friend says that changing electric and magnetic fields underlie the production of light
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agree with friend
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The primary of a transformer connected to 200 V has 100 turns. The secondary has 10 turns. This is a step-down transformer
